JP2011013474A - Optical signal transmission/reception device, and optical signal transmission/reception method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical signal transmission/reception device and method by which a multiplicity can be enhanced, without significantly shortening the distances among symbols.SOLUTION: The transmission device assigns successive n-bit signals of a data signal string to one of 2types of SOPs (state of polarization) by use of data converter. The transmission device transmits two SOPs as a probe, the two SOPs being orthogonal to each other in Stokes vector repression, excepting the 2types. The reception device includes a polarization controller for converting the SOPs of a reception optical signal; and a polarization controller for analyzing the SOPs of an output optical signal of the polarization controller by use of an SOP analyzer and for controlling the polarization controller based on the information. The SOP analyzer analyzes the SOPs of the probe, and the polarizer controller is controlled so as to convert the SOPs into the original SOPs; and thereafter, an SOP data string of the reception optical signal is output to the data converter, and it is restored to the original data signal string.

Description

  The present invention relates to an optical signal transmission / reception device and an optical signal transmission / reception method for transmitting multi-value bit information in a state of polarization (SOP).

  As a multiplexing method in a large-capacity transmission system, time-division multiplexing (TDM: Time-Domain Multiplexing) has been the mainstream up to a transmission rate of 10 Gbit / s. In order to reduce the symbol rate as a countermeasure against polarization mode dispersion (PMD), QPSK, which is a multiplexing method using phase information of optical signals, has been used in higher speed 40 Gbit / s systems (non-patent) Reference 1).

  In higher-speed 100 Gbit / s systems, which are being studied for practical use in the future, it is necessary to increase the multiplicity and suppress the increase in symbol rate due to the problem of the operation speed of electric circuits. A system has been proposed. Among them, there are xPSK (Non-Patent Document 2) as a high-speed multiplexing method using phase information, xAPSK, xQAM (Non-Patent Document 3), etc. using amplitude information in addition to phase information. Also, a polarization multiplexing / demultiplexing system that transmits independent signals with orthogonal polarization is often used together. Non-patent documents 4 and 5 are referred to in the description of the embodiments.

Kataoka, T .; Matsuoka, S .; Matsuda, T .; Maeda, H .; Sakaida, N .; Kubo, T .; Kotanigawa, T .; Kawasaki, T., “Field transmission by using a commercially-ready 43 Gbit / s DWDM system using RZ-DQPSK transponders in high PMD installed fiber ”, OFC2007, JThA45, (2007) R. Freund, D.-D. Gro, M. Seimetz, L. Molle, C. Caspar, “30 Gbit / s RZ-8-PSK Transmission over 2800 km Standard Single Mode Fiber without Inline Dispersion Compensation”, OFC2008, OMI5 , (2008) M. Nakazawa, “CHALLENGES TO FDM-QAM COHERENT TRANSMISSION WITH ULTRAHIGH SPECTRAL EFFICIENCY”, ECOC2008, Tu.1.E.1, (2008) RMA AZZAM, “Longitudinal polarization-dependent coupling of light from an optical fiber to a side-bonded planar proximity detector: application to integrated azimuthally distributed multidetector photopolarimeters”, IEEE Photon. Technol. Lett., Vol.2, No.12, ( 1990) Betti, S .; Curti, T .; Daino, B .; De Marchis, G .; Iannone, E .; “STATE OF POLARISATION AND PHASE NOISE INDEPENDENT COHERENT OPTICAL TRANSMISSION SYSTEM BASED ON STOKES PARAMETER DETECTION”, Electron. Lett., Vol.24, No.23, (1988)

  In the multilevel modulation / demodulation method in which the state of each signal such as PSK, APSK, QAM, etc. is represented by signal points on a two-dimensional phase plane, the symbol rate decreases due to the multiplexing effect as the multiplicity increases. The reception characteristics are advantageous. However, since the rate at which the inter-code distance is reduced is larger than the rate at which the symbol rate is reduced, there is a problem that the reception sensitivity decreases as the multiplicity increases even at the same bit rate.

  Further, the conventional polarization multiplexing / demultiplexing system treats orthogonal polarizations as two independent modes, and no further multiplexing has been studied.

  The present invention provides an optical signal transmission / reception device and an optical signal transmission / reception method capable of increasing multiplicity, which represents multi-level bit information in the polarization state (SOP) of light and greatly reduces the intersymbol distance. Objective.

According to a first aspect of the present invention, a data converter for converting an input data signal string into an SOP data string corresponding to a polarization state (SOP), a signal light source, and output light of the signal light source are output from the data converter. A transmission device having a polarization modulator that modulates with an SOP data sequence, and an optical signal output from the transmission device are received via an optical fiber transmission line, and an SOP data signal sequence is analyzed by analyzing the SOP of the received optical signal. In the optical signal transmission / reception apparatus including the SOP analyzer that outputs the SOP and the data converter that converts the SOP data sequence into the data signal sequence, the transmission device uses the data converter to continue the data signal sequence. An n-bit signal to be assigned is assigned to one of 2 ⁿ types of SOPs, and two SOPs orthogonal to each other in terms of Stokes vector representation other than the 2 ⁿ types are transmitted as probes, and a receiving apparatus Is a polarization controller that converts the SOP of the received optical signal, and a polarization controller controller that analyzes the SOP of the output optical signal of the polarization controller by the SOP analyzer and controls the polarization controller based on the information. The SOP analyzer analyzes the SOP of the probe and controls the polarization controller controller so as to convert it to the original SOP, and then outputs the SOP data string of the received optical signal to the data converter. It is the structure which restores to a signal sequence.

Transmission apparatus in an optical signal transmission and reception apparatus of the first invention, allocates a n-bit signal for successive data signal sequence in the data converter to one of the 2 ⁿ kinds of SOP including strength information, Stokes outside the 2 ⁿ kinds It is good also as a structure which transmits two SOP orthogonal to a vector expression as a probe.

According to a second aspect of the present invention, a data converter for converting an input data signal string into an SOP data string corresponding to a polarization state (SOP), a signal light source, and output light of the signal light source are output from the data converter. A transmission device having a polarization modulator that modulates with an SOP data sequence, and an optical signal output from the transmission device are received via an optical fiber transmission line, and an SOP data signal sequence is analyzed by analyzing the SOP of the received optical signal. In the optical signal transmission / reception apparatus including the SOP analyzer that outputs the SOP and the data converter that converts the SOP data sequence into the data signal sequence, the transmission device uses the data converter to continue the data signal sequence. An n-bit signal to be assigned is assigned to one of 2 ⁿ types of SOPs including intensity information, and two SOPs orthogonal to each other in the Stokes vector representation other than the 2 ⁿ types are transmitted as probes. The receiving apparatus includes a 90-degree hybrid that causes the received optical signal and local light to interfere with each other and outputs four light intensity signals, and the SOP analyzer analyzes the SOP of the probe from the output of the 90-degree hybrid to obtain the original SOP. In this configuration, a conversion matrix to be converted into a signal is obtained, an SOP data sequence obtained by using the conversion matrix for the received optical signal is output to a data converter, and the original data signal sequence is restored.

In a third aspect of the invention, the data signal sequence input to the transmitter is converted into an SOP data sequence corresponding to the polarization state (SOP), input to the polarization modulator, and an optical signal modulated by the SOP data sequence is converted. A process of transmitting and receiving an optical signal by a receiving device via an optical fiber transmission line, analyzing the SOP of the received optical signal, generating an SOP data signal sequence, and converting the SOP data sequence into a data signal sequence In the optical signal transmission / reception method to be performed, the transmission device assigns a continuous n-bit signal of a data signal sequence to one of 2 ⁿ types of SOPs by a data converter, and orthogonally expresses Stokes vectors other than 2 ⁿ types 2 The SOP is transmitted as a probe, and the receiving device analyzes the SOP of the output optical signal of the polarization controller that converts the SOP of the received optical signal with the SOP analyzer, and based on the information A polarization controller controller that controls the polarization controller, and the SOP analyzer analyzes the SOP of the probe and controls the polarization controller controller to convert it to the original SOP, and then the SOP of the received optical signal The data string is output to the data converter and restored to the original data signal string.

In the transmitter according to the third aspect of the invention, a data converter assigns a continuous n-bit signal of a data signal sequence to one of 2 ⁿ types of SOPs including intensity information, and orthogonally expresses the Stokes vector in addition to the 2 ⁿ types Two SOPs to be transmitted are transmitted as probes.

In a fourth aspect of the invention, the data signal sequence input to the transmitter is converted into an SOP data sequence corresponding to the polarization state (SOP), input to the polarization modulator, and the optical signal modulated by the SOP data sequence is converted. A process of transmitting and receiving an optical signal by a receiving device via an optical fiber transmission line, analyzing the SOP of the received optical signal, generating an SOP data signal sequence, and converting the SOP data sequence into a data signal sequence In the optical signal transmission / reception method to be performed, the transmission apparatus assigns a continuous n-bit signal of a data signal sequence to one of 2 ⁿ types of SOPs including intensity information by a data converter, and expresses the Stokes vector expression other than the 2 ⁿ types The SOP analyzer transmits a 90-degree hybrid that outputs four light intensity signals by causing the received optical signal and local light to interfere with each other, and the SOP analyzer is a 90-degree hybrid. The SOP of the probe is analyzed from the output of the signal to obtain a conversion matrix for conversion to the original SOP, and the SOP data sequence obtained by using the conversion matrix for the received optical signal is output to the data converter, and the original data Restore to signal sequence.

  In the present invention, multi-value bit information can be expressed by the polarization state (SOP) of light. Whereas multiplexing methods such as PSK, APSK, QAM, etc. represent multi-level bit information with one phase information and amplitude information, the present invention uses phase information and amplitude information of each polarization, so that the conventional two-dimensional From multiplexing on a plane to multiplexing in a three-dimensional space, the multiplicity can be increased without greatly reducing the intersymbol distance.

As shown in FIG. 1, the polarization state of the light is determined by the polarization ellipticity χ (= tan ⁻¹ (b / a)) due to the phase relationship of the orthogonal light, the main axis azimuth ψ by the relative amplitude, and the synthesis of each amplitude As a result, the strength r changes. (Χ, ψ, r) can be converted into Stokes parameters (S ₁ , S ₂ , S ₃ ) by the following equation (1).
S ₁ = r cos (2χ) cos (2ψ)
S ₂ = r cos (2χ) sin (2ψ)
S ₃ = rsin (2χ) (1)

  By arranging signal points at three-dimensional points represented by the Stokes parameters, multiplexing in three dimensions becomes possible.

  However, each SOP given to the signal light by the transmitting device rotates by propagating through the optical fiber, but this rotation becomes a problem when demodulating by the receiving device. In the present invention, by utilizing the fact that the relative relationship of each SOP does not change compared to the symbol rate, two SOPs orthogonal to each other in the Stokes vector representation are used as probes. By giving each SOP a transformation that rotates to match the SOP, the SOP data sequence modulated in the transmitter can be restored.

It is a figure which shows the polarization state of light. It is a figure which shows the structural example of Example 1 of the optical signal transmitter / receiver of this invention. 3 is a diagram illustrating a configuration example of a polarization modulator 13. FIG. It is a figure which shows the mode of the modulated light of Example 1. FIG. It is a figure which shows the mode of the modulated light of Example 2. FIG. It is a figure which shows the structural example of Example 3 of the optical signal transmitter / receiver of this invention.

FIG. 2 shows a configuration example of Embodiment 1 of the optical signal transmitting / receiving apparatus of the present invention.
In the figure, the transmission device 10 is composed of a data converter 11, a signal light source 12, and a polarization modulator 13. The receiving device 20 includes a polarization controller 21, an optical / electrical converter (O / E) 22, an SOP analyzer 23, a polarization controller controller 24, and a data converter 25. The SOP analyzer 23 includes an analog / digital converter.

FIG. 3 shows a configuration example of the polarization modulator 13.
In the figure, the polarization modulator 13 includes a polarization separator 131, phase modulators 132 and 133, intensity modulators 134 and 135, and a polarization multiplexer 136. The polarization ellipticity is controlled by generating a phase difference between orthogonal polarizations separated by the polarization separator 131 by the voltage applied to the phase modulators 132 and 133. The principal axis azimuth is controlled by changing the intensity of the orthogonal polarization by the voltage applied to the intensity modulators 134 and 135.

  The data converter 11 of the transmission apparatus 10 converts the input data signal sequence into one SOP information of Table 1 every 4 bits, and the phase modulators 132 and 133 and the intensity modulators 134 and 135 of the polarization modulator 13. To enter. The polarization modulator 13 sets the SOP of the output light of the signal light source 12 based on the SOP information corresponding to the data signal sequence. The state of the modulated light is shown in FIG.

Here, each Stokes vector is normalized. Two orthogonal Stokes parameters U ₀ = (0, 1, 0) and V ₀ = (-1, 0, 0) used as probes are respectively U = (u ₁ , u ₂ , u ₃ ) = ( Suppose that χ ₁ , ψ ₁ , 1) and V = (v ₁ , v ₂ , v ₃ ) = (χ ₂ , ψ ₂ , 1). In order to return U and V to U ₀ and V ₀ , first, U is changed to U ′ using the rotation matrix T ₁ centered on the S ₁ axis and the rotation matrix T ₃ centered on the S ₃ axis expressed by Equation (2). Convert and convert V to V ′.

At this time, U ′ = T ₁ , T ₃ , U = (0, 1, 0). Since U'⊥V 'than U よ り V,
V ′ = (v ₁ ′, 0, v ₃ ′) = (χ ₂ ′, ψ ₂ ′, 1) (where χ ₂ ′ = 0 or π / 2)
It is expressed. Further, V ′ is converted into V ″ = T ₂ · V ′ = (− 1, 0, 0) using T ₂ represented by the equation (3).

As described above, each SOP data sequence after reception is converted by the polarization controller 21 of the receiving device 20 using the matrices T ₂ , T _1, and T ₃ to restore the SOP data sequence at the time of transmission. Specifically, an SOP analyzer 23 observes a signal after passing through the polarization controller 21 composed of a quarter wave plate for changing the ellipticity and a half wave plate for changing the principal axis azimuth. The polarization controller 21 is controlled via the polarization controller controller 24 so that the SOP of each probe is U ′ = (0, 1, 0) and V ″ = (− 1, 0, 0). When the data string is received, the setting of the polarization controller 22 is fixed.

  The SOP analyzer 23 determines the SOP data string from the output of the fixed polarization controller 21 and outputs it to the data converter 25, and the data converter 25 restores the data signal string according to Table 1. As a method for determining the SOP of the received signal in the SOP analyzer 23, for example, there is a method described in Non-Patent Document 4.

  The configurations of the transmission apparatus 10 and the reception apparatus 20 of the optical signal transmission / reception apparatus of the present embodiment are the same as those of the first embodiment shown in FIG.

  The data converter 11 of the transmission apparatus 10 of this embodiment converts the input data signal sequence into one SOP information in Table 2 to which light intensity information is added every 5 bits, and the polarization modulator 13 shown in FIG. Are input to the phase modulators 132 and 133 and the intensity modulators 134 and 135. The polarization modulator 13 sets the SOP of the output light of the signal light source 12 based on the SOP information corresponding to the data signal sequence. That is, the polarization ellipticity is controlled by generating a phase difference of orthogonal polarizations by the voltage applied to the phase modulators 132 and 133. The intensity of orthogonal polarized waves is changed by the voltage applied to the intensity modulators 134 and 135 to control the light intensity in addition to the principal axis azimuth. The state of the modulated light is shown in FIG.

  Since the SOP determination in the receiving apparatus 20 includes light intensity information, the method for restoring the transmission SOP data sequence using the probe and the SOP determination by the SOP analyzer 22 are the same as those in the first embodiment. The data converter 25 restores the data signal sequence according to Table 2.

FIG. 6 shows a configuration example of Embodiment 3 of the optical signal transmitting / receiving apparatus of the present invention.
In the figure, the transmission device 10 is composed of a data converter 11, a signal light source 12, and a polarization modulator 13. The receiving apparatus 20 includes a 90-degree hybrid 26, a local light source 27, an optical / electrical converter (O / E) 22, an SOP analyzer 28, and a data converter 25. The SOP analyzer 28 includes an analog / digital converter.

  Similarly to the second embodiment, the data converter 11 of the transmission apparatus 10 according to the present embodiment converts the input data signal sequence into one SOP information in Table 2 in which light intensity information is added every 5 bits. Input to the modulator 13. The polarization modulator 13 sets the SOP of the output light of the signal light source 12 based on the SOP information corresponding to the data signal sequence. That is, the polarization ellipticity is controlled by generating a phase difference between orthogonal polarizations by the voltage applied to the phase modulators 132 and 133 in FIG. The intensity of orthogonal polarized waves is changed by the voltage applied to the intensity modulators 134 and 135 to control the light intensity in addition to the principal axis azimuth.

In the receiving device 20, the four light intensity signals obtained by using the local light of the local light source 27 and the 90-degree hybrid 26 are converted into electrical signals by the O / E 22, respectively, and then analog / digital by the SOP analyzer 28. The SOP is determined by digital signal processing from the converted signal. SOP determination, first after obtaining a transformation matrix T ₂ · T ₁ · T ₃ to return the probe receiving SOP to the transmission SOP, at the time of transmission using the transformation matrix T ₂ · T ₁ · T ₃ with respect to the received signal Restore the SOP data string. The data converter 25 restores the data signal sequence according to Table 2. As a method for determining the SOP of the received signal in the SOP analyzer 28, for example, there is a method described in Non-Patent Document 5.

DESCRIPTION OF SYMBOLS 10 Transmission apparatus 11 Data converter 12 Signal light source 13 Polarization modulator 20 Reception apparatus 21 Polarization controller 22 Optical / electrical converter (O / E)
23, 28 SOP analyzer 24 Polarization controller controller 25 Data converter 26 90 degree hybrid 27 Local light source

Claims (6)

A data converter that converts an input data signal sequence into an SOP data sequence corresponding to a polarization state (SOP), a signal light source, and an output light of the signal light source is modulated by an SOP data sequence output from the data converter. A transmitter having a polarization modulator;
An SOP analyzer that receives an optical signal output from the transmission device via an optical fiber transmission line, analyzes the SOP of the received optical signal, and outputs an SOP data signal sequence, and the SOP data sequence as a data signal sequence An optical signal transmitting / receiving device comprising: a receiving device having a data converter for converting into:
The transmitter assigns a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs by the data converter, and probes two SOPs orthogonal to each other in Stokes vector representation other than the 2 ⁿ types And send as
The receiving device analyzes the SOP of the output optical signal from the polarization controller for converting the SOP of the received optical signal by the SOP analyzer, and controls the polarization controller based on the information. A controller controller, the SOP analyzer analyzes the SOP of the probe, controls the polarization controller controller to convert to the original SOP, and then converts the SOP data sequence of the received optical signal to the SOP An optical signal transmitting / receiving apparatus characterized in that it is configured to output to a data converter and restore the original data signal sequence. The optical signal transmitting / receiving apparatus according to claim 1.
In the transmitter, the data converter allocates a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs including intensity information, and other than the 2 ⁿ types, 2 orthogonal to the Stokes vector representation. An optical signal transmitting / receiving apparatus characterized in that one SOP is transmitted as a probe. A data converter that converts an input data signal sequence into an SOP data sequence corresponding to a polarization state (SOP), a signal light source, and an output light of the signal light source is modulated by an SOP data sequence output from the data converter. A transmitter having a polarization modulator;
An SOP analyzer that receives an optical signal output from the transmission device via an optical fiber transmission line, analyzes the SOP of the received optical signal, and outputs an SOP data signal sequence, and the SOP data sequence as a data signal sequence An optical signal transmitting / receiving device comprising: a receiving device having a data converter for converting into:
In the transmitter, the data converter allocates a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs including intensity information, and other than the 2 ⁿ types, 2 orthogonal to the Stokes vector representation. It is a configuration that transmits one SOP as a probe,
The receiver includes a 90-degree hybrid that outputs four light intensity signals by causing the received optical signal and local light to interfere with each other, and the SOP analyzer analyzes the SOP of the probe from the output of the 90-degree hybrid, A conversion matrix to be converted into SOP is obtained, and the SOP data sequence obtained by using the conversion matrix for the received optical signal is output to the data converter and restored to the original data signal sequence. An optical signal transmitting / receiving apparatus characterized by the above. The data signal sequence input to the transmission device is converted into an SOP data sequence corresponding to the polarization state (SOP), input to the polarization modulator, and an optical signal modulated by the SOP data sequence is transmitted.
Light that receives the optical signal by a receiving device via an optical fiber transmission line, analyzes the SOP of the received optical signal, generates an SOP data signal sequence, and converts the SOP data sequence into a data signal sequence In the signal transmission / reception method,
The transmitter assigns a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs by the data converter, and probes two SOPs orthogonal to each other in Stokes vector representation other than the 2 ⁿ types Send as
The receiving device analyzes the SOP of the output optical signal from the polarization controller for converting the SOP of the received optical signal by the SOP analyzer, and controls the polarization controller based on the information. A controller controller, the SOP analyzer analyzes the SOP of the probe, controls the polarization controller controller to convert to the original SOP, and then converts the SOP data sequence of the received optical signal to the SOP An optical signal transmission / reception method comprising: outputting to a data converter and restoring the original data signal sequence. The optical signal transmission / reception method according to claim 4,
In the transmitter, the data converter allocates a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs including intensity information, and other than the 2 ⁿ types, 2 orthogonal to the Stokes vector representation. An optical signal transmission / reception method characterized by transmitting one SOP as a probe. The data signal sequence input to the transmission device is converted into an SOP data sequence corresponding to the polarization state (SOP), input to the polarization modulator, and an optical signal modulated by the SOP data sequence is transmitted.
Light that receives the optical signal by a receiving device via an optical fiber transmission line, analyzes the SOP of the received optical signal, generates an SOP data signal sequence, and converts the SOP data sequence into a data signal sequence In the signal transmission / reception method,
In the transmitter, the data converter allocates a continuous n-bit signal of the data signal sequence to one of 2 ⁿ types of SOPs including intensity information, and other than the 2 ⁿ types, 2 orthogonal to the Stokes vector representation. Send one SOP as a probe,
The receiver includes a 90-degree hybrid that outputs four light intensity signals by causing the received optical signal and local light to interfere with each other, and the SOP analyzer analyzes the SOP of the probe from the output of the 90-degree hybrid, A conversion matrix to be converted into SOP is obtained, and an SOP data sequence obtained by using the conversion matrix with respect to the received optical signal is output to the data converter and restored to the original data signal sequence. Optical signal transmission / reception method.

Images