JP2007267001A - Dispersion pre-equally dividing optical transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion pre-equally dividing optical transmitter for reducing an insertion loss by making the output optical signal strength of each optical modulation unit almost equal, while two optical modulation units of an I-channel and a Q-channel in a nest type optical modulation device are driven always with almost equal magnitudes. <P>SOLUTION: A transmission data sequence arithmetic processing device for generating two sequence data, an optical phase adjustment unit 21 for driving an optical modulation unit 20a by using an I-channel out of two sequence data and driving an optical modulation unit 20b by using a Q-channel, giving an orthogonal relation to two modulation optical signals, and an optical phase modulation device for transmitting an optical signal, which has been subjected to dispersion pre-equally dividing optical, are provided. The transmission data sequence arithmetic processing device includes at least a dispersion inverse function arithmetic means 10 for subjecting the entered transmission sequence original data to the inverse function processing of wavelength dispersion and the inverse function processing of an optical modulation device transfer function, and a coordinate inverse arithmetic means for subjecting the complex data obtained from the dispersion inverse function arithmetic means 10 to the coordination rotation of a prescribed angle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention always drives the two optical modulators of the I-channel and Q-channel of the nested optical modulator with approximately the same amplitude, and makes the output optical signal intensity of each optical modulator approximately equal. The present invention relates to a dispersion pre-equalized optical transmitter that reduces insertion loss.

  In a long-distance optical communication system, a technique for more efficiently compensating for the chromatic dispersion of a transmission line is important in order to reduce the cost of the system and easily perform system upgrade by increasing the transmission rate. For example, it is possible to reduce the cost of the system by reducing the dispersion compensating fiber and the optical amplifier used for the loss compensation. In addition, although the chromatic dispersion tolerance varies depending on the transmission rate and modulation format, the transmission rate and modulation format can be reduced by using no dispersion compensation fiber or using only a few types of dispersion compensation fiber in any transmission system. It is possible to adopt a transmission path configuration that does not depend on the result, and as a result, it is easy to upgrade an existing system and to realize a system in which a plurality of modulation methods are mixed.

  As one measure for obtaining the above effect, when the amount of dispersion pre-equalization is small (for example, about ˜2000 ps / nm for a 10 Gb / s optical signal), the transmission side depends on the chromatic dispersion of the transmission path. There is a method of applying pre-chirp based on phase modulation (see, for example, Patent Document 1 and Patent Document 2). However, in the distributed pre-equalization method using pre-chirp, since the amount of distributed pre-equalization is small, the above-mentioned system cost reduction and ease of upgrade are not dramatically promoted. Here, as a method of performing very large dispersion pre-equalization such as 20000 to 40,000 ps / nm for 10 Gb / s, the effect of chromatic dispersion having the same absolute value but the opposite sign with respect to the chromatic dispersion of the transmission line. Distributed pre-equalization transmission schemes for transmitting optical signals to which are added in advance have been actively studied (see, for example, Non-Patent Document 1 and Non-Patent Document 2).

  A conventional dispersion pre-equalized optical transmitter will be described with reference to the drawings. FIG. 5 is a block diagram showing a configuration of a transmission data sequence arithmetic processor of a conventional distributed pre-equalization optical transmitter. FIG. 6A is a block diagram showing a configuration of an optical modulator of a conventional dispersion pre-equalization optical transmitter. FIG. 6B shows an orthogonal relationship between the optical electric fields.

  The conventional dispersion pre-equalization optical transmitter is provided with a transmission data sequence arithmetic processor shown in FIG. 5 and an optical modulator shown in FIG.

  In FIG. 5, a transmission data sequence arithmetic processing unit of a conventional dispersion pre-equalization optical transmitter includes a dispersion inverse function calculation unit 10, modulator inverse function calculation units 12a and 12b, D / A converters 13a and 13b, Amplifiers 14a and 14b are provided.

  In FIG. 6A, the optical modulator of the conventional dispersion pre-equalization optical transmitter includes MZ (Mach-Zehnder) type optical modulation units 20a and 20b, an optical phase adjustment unit 21, and a DC bias control means. 22a, 22b, 22c, optical demultiplexing means 23, and optical multiplexing means 24 are provided.

  In the conventional example, as shown in FIG. 5, an inverse function calculation of the chromatic dispersion of the transmission line and an inverse function calculation of the transfer function of the optical modulator are performed on the transmission sequence original data by the dispersion inverse function calculation means 10. By driving the I / Q optical modulator using two series of data (I-channel, Q-channel), an optical signal subjected to dispersion pre-equalization is transmitted.

  At this time, as the inverse function calculation of the chromatic dispersion of the transmission line, the chromatic dispersion of the transmission line has the same absolute value and the sign is reversed, and the transmission function is multiplied by the transmission function of the chromatic dispersion or the impulse obtained from the same transfer function. A general method is to obtain a complex data sequence by convolution of a response and a transmission data sequence. In general, the response characteristics of electrical / optical conversion are not linear, so in order to generate an ideal optical signal, the inverse function of the modulator is usually used to correct the response characteristics of electrical / optical conversion. Means 12a and 12b are added. Further, when each of the above operations is performed by digital arithmetic processing, an analog signal for driving the optical modulator is obtained through the D / A converters 13a and 13b and the amplifiers 14a and 14b.

  Optical I / Q modulation is performed, for example, by driving each MZ type optical modulator 20a, 20b with an I-channel and a Q-channel with a nested optical modulator configured as shown in FIG. The nest type optical modulator used for DQPSK (Differential Quadrature Phase Shift Keying) modulation performs π / 2 phase shift by the optical phase adjustment unit 21, and thus, from I / Q two series data, I-channel Since it is possible to generate a complex optical electric field in which the modulated optical signal and the modulated optical signal in the Q-channel are orthogonal, it can be used as an optical modulator for dispersion pre-equalization transmission (for example, patent Reference 3).

  By the way, in FIG. 5, assuming that a zero-chirp NRZ (Non-Return-to-Zero) optical signal is transmitted as a transmission data sequence, the relationship between the real part and the imaginary part as a complex optical field is, for example, a pre-equalization amount Is zero, the imaginary part component of the drive signal = 0. Here, if the complex data is directly assigned to the orthogonal I-channel and Q-channel in the nested optical modulator, as shown in FIG. 6B, I-channel = data and Q-channel = 0. Modulation will be performed. This means that one of the optical modulators of the nested optical modulator is used in a quenched state, and the insertion loss of the nested optical modulator may increase by 3 dB.

Japanese Patent Laid-Open No. 06-303205 JP 05-110516 A JP-T-2004-516743 D. McGhan, et. al. “5120-km RZ-DPSK Transmission Over G.652 Fiber at 10 Gb / s Without Optical Dispersion Compensation” IEEE Photon. Technol. Lett. , Vol. 18, no. 2, 400, 2006. K. Roberts, et. al. “Electronic Precompensation of Optical Nonlinearity” IEEE Photon. Technol. Lett. , Vol. 18, no. 2, 403, 2006.

  As described above, using a nested optical modulator for I / Q modulation as an optical modulator for dispersion pre-equalization, the real part of the result of performing an inverse function calculation of the chromatic dispersion of the transmission line, When the complex optical electric field is generated by assigning the imaginary part to the I-channel and the Q-channel, respectively, there is a problem that an excess loss of 3 dB may occur depending on the modulation format and the dispersion amount of pre-equalization. .

  The present invention has been made to solve the above-described problems, and its purpose is to always drive the two optical modulators of the nested optical modulator of I-channel and Q-channel with approximately the same amplitude. Thus, a dispersion pre-equalized optical transmitter capable of reducing the insertion loss is obtained by setting the output optical signal intensities of the respective optical modulation units to approximately the same level.

  The dispersion pre-equalization optical transmitter according to the present invention uses a transmission data sequence arithmetic processor for generating two series of data of I channel and Q channel, and first I channel data using the I channel data of the two series of data. And the second optical modulator using the Q-channel data, and the optical phase adjuster is orthogonal to the two modulated optical signals from the first and second optical modulators. A distributed pre-equalized optical transmitter having an optical modulator that transmits an optical signal that has been subjected to dispersion pre-equalization, wherein the transmission data sequence arithmetic processing unit is configured to input input transmission sequence original data Dispersion inverse function computing means for performing inverse function computation of the chromatic dispersion of the transmission line and inverse function of the optical modulator transfer function, and coordinates of a predetermined angle with respect to the complex data obtained from the dispersion inverse function computing means Coordinate transformation calculation means for rotation Hints at least, based on the coordinate data converted from the coordinate conversion calculation means, and generates the data of the two series of I and Q channels.

  The dispersion pre-equalization optical transmitter according to the present invention always drives the two optical modulators of the nested optical modulator of I-channel and Q-channel with substantially the same amplitude, and outputs the optical signal intensity of each optical modulator. By making the values approximately the same, there is an effect that the insertion loss can be reduced.

Embodiment 1 FIG.
A dispersion pre-equalized optical transmitter according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a block diagram showing a configuration of a transmission data sequence arithmetic processor of a distributed pre-equalization optical transmitter according to Embodiment 1 of the present invention. FIG. 2A is a block diagram showing the configuration of the optical modulator of the dispersion pre-equalization optical transmitter according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  The dispersion pre-equalized optical transmitter according to the first embodiment is provided with a transmission data sequence arithmetic processor shown in FIG. 1 and an optical modulator shown in FIG.

  In FIG. 1, a transmission data sequence arithmetic processing unit of the dispersion pre-equalization optical transmitter according to the first embodiment includes a dispersion inverse function calculating means 10, a coordinate transformation calculating means 11, a modulator inverse function calculating means 12a, 12b, D / A converters 13a and 13b, and amplifiers 14a and 14b are provided.

  2A, the optical modulator of the dispersion pre-equalization optical transmitter according to the first embodiment includes MZ (Mach-Zehnder) type optical modulation units 20a and 20b, an optical phase adjustment unit 21, and the like. DC bias control means 22a, 22b, 22c, optical demultiplexing means 23, and optical multiplexing means 24 are provided.

  Next, the operation of the dispersion pre-equalized optical transmitter according to the first embodiment will be described with reference to the drawings.

  First, an inverse function calculation of the chromatic dispersion of the transmission line and an inverse function calculation of the optical modulator transfer function are performed by the dispersion inverse function calculation means 10 on the transmission sequence original data. As the inverse function calculation of the chromatic dispersion of the transmission line, the chromatic dispersion of the transmission line and the absolute value are the same, but the sign of the chromatic dispersion is multiplied by the transmission sequence source data or the impulse response obtained from the same transfer function. A method of obtaining a complex data string by convolution with transmission sequence original data is generally used, and these operations can be easily realized by digital arithmetic processing or an analog FIR filter.

  Next, the coordinate conversion calculation means 11 performs coordinate conversion calculation on complex data obtained after calculating the inverse function of chromatic dispersion. For example, when the input signal of the coordinate transformation calculation means 11 is Din = (Dr (t), Di (t)) and the coordinate rotation of the angle θ is performed as the coordinate transformation calculation, the output signal Dout is expressed by the following formula (1 ) Can be expressed as:

  Dout = [Dr (t) · cos (θ) + Di (t) · sin (θ), −Dr (t) · sin (θ) + Di (t) · cos (θ)] Equation (1)

  Dr (t) represents a real part and Di (t) represents an imaginary part. In addition, the first half {Dr (t) · cos (θ) + Di (t) · sin (θ)} on the right side of Expression (1) corresponds to the I′− channel, and the second half {−Dr (t) on the right side. Sin (θ) + Di (t) · cos (θ)} corresponds to the Q′− channel.

  Next, the data after the coordinate conversion is corrected by the modulator inverse function calculation means 12a and 12b by the inverse function of the response characteristic of the optical modulator. Further, when each of the above calculations is performed by digital calculation processing, D / A converters 13a and 13b and amplifiers 14a and 14b are arranged in the subsequent stage to provide two series of optical modulator drive data (I′-channel, Q '-Channel). The modulator inverse function calculating means 12a and 12b are provided in the subsequent stage of the dispersion inverse function calculating means 10 or the coordinate transformation calculating means 11, and are the inverse function of the response characteristics of the electro-optic conversion of the optical modulator and the signal amplitude of the data series. Correct.

  Next, the relationship between the data obtained by the transmission data sequence arithmetic processor and the modulated optical signal will be described with reference to FIGS. 2 (a) and 2 (b).

  The difference between the first embodiment and the conventional example is that the driving of the MZ type optical modulators 20a and 20b is performed in the I'-channel and the Q'-channel that have undergone the coordinate conversion calculation.

  For example, when coordinate rotation of π / 4 is performed as the coordinate conversion calculation, the output signal Dout in the equation (1) can be expressed as the following equation (2).

  Dout = [Dr (t) / √2 + Di (t) / √2, −Dr (t) / √2 + Di (t) / √2] Equation (2)

  It can be seen that even if Di (t) = 0, two series of data with approximately equal amplitude can be obtained as Dout. Further, even when the amount of dispersion pre-equalization is increased and the ratio of Dr (t) and Di (t) is changed, the change in the I′-channel and the Q′-channel is the same. The amplitudes of the I′-channel and the Q′-channel can be kept substantially constant regardless of the conversion amount. As a result, as shown in FIG. 2 (b), each MZ type light modulation unit 20a, 20b can be driven with a substantially equal amplitude regardless of the pre-equalization dispersion amount. There is no need to use it in the extinguished state, and the insertion loss can be improved up to 3 dB compared to the case where coordinate conversion is not performed. Also in this case, the relationship of the complex electric field is the (I′-channel, Q′−) of the system rotated by π / 4 coordinate as compared with the (I-channel, Q-channel) relationship without coordinate conversion. It is self-evident that the orthogonal relationship is maintained as the channel) and the property of the optical signal as a complex electric field does not change.

  Therefore, the configuration shown in FIGS. 1 and 2 can improve the insertion loss of the nested optical modulator by a maximum of 3 dB while maintaining the orthogonal relationship of the transmitted optical signals.

  That is, the dispersion pre-equalization optical transmitter according to the first embodiment includes a transmission data sequence arithmetic processor for generating two series of data of I channel and Q channel, and I channel data among the two series of data. Is used to drive the MZ light modulator 20a (first light modulator), and the MZ light modulator 20b (second light modulator) is driven using the Q channel data. An optical modulator for transmitting an optical signal that has been subjected to dispersion pre-equalization so that the optical phase adjustment unit 21 has an orthogonal relationship with the two modulated optical signals from the modulation units 20a and 20b, and the transmission data sequence calculation process The unit obtains from the dispersion inverse function computing means 10 for performing the inverse function computation of the chromatic dispersion of the transmission line and the inverse function computation of the optical modulator transfer function with respect to the input transmission sequence original data, and the dispersion inverse function computing means 10. Complex data And at least a coordinate transformation calculation means 11 that performs coordinate rotation of a predetermined angle, and generates two series of data of I channel and Q channel based on the coordinate transformed data from the coordinate transformation calculation means 11. is there. The transmission data series arithmetic processing unit is provided after the inverse dispersion function calculating means 10 or the coordinate transformation calculating means 11, and corrects the signal amplitude of the data series with the inverse function of the electro-optical conversion response characteristic of the optical modulator. Modulator inverse function calculation means 12a and 12b are further included.

Embodiment 2. FIG.
A dispersion pre-equalized optical transmitter according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration of a transmission data sequence arithmetic processor of the distributed pre-equalization optical transmitter according to Embodiment 2 of the present invention. The configuration of the optical modulator is the same as that in the first embodiment.

  In FIG. 3, the transmission data sequence arithmetic processing unit of the dispersion pre-equalization optical transmitter according to the second embodiment has a branching unit 31 added thereto, and the distributed inverse function calculating unit 10 has a real part calculating unit 32 and an imaginary part calculating unit. And means 33. In addition, the component which has the same function as FIG. 1 attaches | subjects the same code | symbol as FIG.

  Next, the operation of the dispersion pre-equalized optical transmitter according to the second embodiment will be described with reference to the drawings.

  FIG. 3 shows a configuration in the case where the present invention is applied to OOK (On-Off Keying) modulation or DPSK (Differential Phase Shift Keying) modulation as a whole. As compared with the first embodiment, the branching means is as described above. 31 has been added.

  In FIG. 3, when transmission sequence original data is input, after branching to the same two data by the branching means 31, only the real part of the distributed inverse function calculation is calculated by the real part calculating means 32 for each. The calculation of only the imaginary part is performed by the imaginary part calculating means 33.

  Next, two new orthogonal data (corresponding to I'-channel and Q'-channel) are generated from the obtained real part and imaginary part data by the coordinate transformation calculation means 11a and 11b. The subsequent data is the same as in the first embodiment.

  Note that, when separate data encoding is required, such as DPSK modulation or Duo-binary modulation, encoded data is input as transmission sequence source data in FIG. In FIG. 3, only one transmission sequence source data is input. However, the branching means 31 may be omitted and the input may be two identical data sequences.

  It goes without saying that the output amplitude of the amplifier, the modulator inverse function calculation parameter, and the DC bias control parameter may be adjusted and optimized according to the modulation format.

  By using the second embodiment, when a dispersion pre-equalized optical transmitter is configured using a nested optical modulator in a modulation format such as OOK or DPSK modulation, insertion loss in the nested optical modulator is reduced. It is possible to reduce the maximum by 3 dB.

  That is, the dispersion pre-equalization optical transmitter according to the second embodiment includes a transmission data sequence arithmetic processing unit that generates two series of data of I channel and Q channel, and I channel data among the two series of data. Is used to drive the MZ light modulator 20a (first light modulator), and the MZ light modulator 20b (second light modulator) is driven using the Q channel data. An optical modulator for transmitting an optical signal that has been subjected to dispersion pre-equalization so that the optical phase adjustment unit 21 has an orthogonal relationship with the two modulated optical signals from the modulation units 20a and 20b, and the transmission data sequence calculation process The branch branches the input transmission sequence original data into the same two transmission sequence original data, and outputs them to the real part calculation means 32 and the imaginary part calculation means 33 constituting the distributed inverse function calculation means 10, respectively. Means 31 and the same Real part computing means 32 for performing only the real part of the inverse function calculation of the chromatic dispersion of the transmission line and the inverse function of the optical modulator transfer function for one of the two transmission series source data, and the same two transmission series An imaginary part computing means 33 that performs computation of only the imaginary part of the inverse function computation of the chromatic dispersion of the transmission line and the inverse function of the optical modulator transfer function, the real part computing means 32, and the imaginary part computation. Coordinate conversion calculation means 11a and 11b that perform coordinate rotation of a predetermined angle with respect to the complex data obtained from the means 33, and based on the coordinate-converted data from the coordinate conversion calculation means 11a and 11b, Two series of Q channel data are generated. The transmission data series arithmetic processing unit is provided in the subsequent stage of the dispersion inverse function calculating means 10 or the coordinate transformation calculating means 11a and 11b, and the signal amplitude of the data series is determined by the inverse function of the response characteristic of electro-optical conversion of the optical modulator. Modulator inverse function calculation means 12a and 12b for correction are further included.

Embodiment 3 FIG.
A dispersion pre-equalized optical transmitter according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing a configuration of a transmission data sequence arithmetic processor of the distributed pre-equalization optical transmitter according to Embodiment 3 of the present invention. The configuration of the optical modulator is the same as that in the first embodiment.

  In FIG. 4, the transmission data sequence arithmetic processing unit of the distributed pre-equalization optical transmitter according to the third embodiment is added with an adding means 41 (41a, 41b), and the distributed inverse function calculating means 10a is a real part calculating means. 32a and an imaginary part computing means 33a, and a distributed inverse function computing means 10b comprises a real part computing means 32b and an imaginary part computing means 33b. In addition, the component which has the same function as FIG. 1, FIG. 3 attaches | subjects the same code | symbol as FIG. 1, FIG.

  In FIG. 4, the basic blocks shown in the second embodiment are arranged in parallel so as to operate even when two different data are input as transmission sequence source data as in DQPSK (Differential Quadrature Phase Shift Keying) modulation. Each block is connected by adding means 41a and 41b.

  In FIG. 4, first, distributed inverse function calculation means 10a and 10b are applied to transmission sequence original data 1 and transmission sequence original data 2, respectively, and coordinate transformation calculation means 11a, 11b, 11c, and 11d are performed. Then, coordinate transformation calculation is performed to generate two series of data corresponding to (I′-channel, Q′-channel).

  Next, I'-channel components and Q'-channel signals that finally drive the optical modulator are added by adding means 41a and 41b with each other's I'-channel components and Q'-channel components. Get.

  Note that DQPSK modulation requires separate data encoding, and two encoded data are input as transmission sequence source data 1 and transmission sequence source data 2 in FIG.

  Further, by making the transmission sequence source data 1 and the transmission sequence source data 2 in FIG. 4 the same data, it is possible to cope with the OOK modulation and the DPSK modulation shown in the second embodiment.

  Furthermore, the amplifier output amplitude, modulator inverse function calculation parameters, and DC bias control parameters may be adjusted and optimized according to the modulation format, as described above.

  Further, the angle of coordinate rotation calculation at the time of coordinate conversion does not need to be particularly π / 4, and may be changed according to the orthogonal component ratio of the output optical signal when the modulation format and the dispersion pre-equalization amount are zero. Needless to say, it is good.

  By using the third embodiment, it is possible to cope with a modulation format represented by DQPSK that orthogonally multiplexes up to two different data, and in the case of dispersion pre-equalization optical transmission, a nested optical modulation is used regardless of the optical modulation format. It is possible to reduce the insertion loss of the device.

  That is, the dispersion pre-equalization optical transmitter according to the third embodiment includes a transmission data sequence arithmetic processor that generates two series of data of I channel and Q channel, and I channel data among the two series of data. Is used to drive the MZ light modulator 20a (first light modulator), and the MZ light modulator 20b (second light modulator) is driven using the Q channel data. An optical modulator for transmitting an optical signal that has been subjected to dispersion pre-equalization so that the optical phase adjustment unit 21 has an orthogonal relationship with the two modulated optical signals from the modulation units 20a and 20b, and the transmission data sequence calculation process The device branches the input transmission sequence original data 1 into the same two transmission sequence original data, each of which constitutes a distributed inverse function calculation means 10a (first distributed inverse function calculation means). 32a, imaginary part operator The branching means 31a that outputs to 33a and the input transmission sequence original data 2 are branched into the same two transmission sequence original data, and each of them is distributed inverse function calculating means 10b (second distributed inverse function calculating means). The real part calculating means 32b and the branching means 31b that output to the imaginary part calculating means 33b and the inverse function calculation of the chromatic dispersion of the transmission line and the optical modulator transfer function for one of the same two transmission sequence source data 1 Real part calculation means 32a for calculating only the real part of the inverse function calculation, inverse function calculation of the wavelength dispersion of the transmission line and inverse function calculation of the optical modulator transfer function for the other of the same two transmission sequence original data 1 Imaginary part computing means 33a for computing only the imaginary part, and coordinate transformation computing means 11a, 11b (for performing coordinate rotation of a predetermined angle on complex data obtained from the real part computing means 32a and the imaginary part computing means 33a) First Coordinate transformation calculation means) and real part calculation for performing only the real part of the inverse function calculation of the chromatic dispersion of the transmission line and the inverse function of the optical modulator transfer function for one of the same two transmission sequence source data 2 Means 32b, and imaginary part computing means 33b for computing only the imaginary part of the inverse function computation of the chromatic dispersion of the transmission line and the inverse function of the optical modulator transfer function with respect to the other of the same two transmission sequence original data 2; , Coordinate transformation computing means 11c, 11d (second coordinate transformation computing means) for performing coordinate rotation of a predetermined angle with respect to the complex data obtained from the real part computing means 32b and the imaginary part computing means 33b, and coordinate transformation computing means 11a and 11c (first and second coordinate transformation calculation means) adder means 41a (first addition means) for adding together I channel components, and coordinate transformation calculation means 11b and 11d (first and second coordinate conversion means) Coordinate transformation calculation means) Addition means 41b (second addition means) for adding the Q channel components from each other, and generates two series of data of I channel and Q channel based on data from the addition means 41a and 41b. is there. The transmission data series arithmetic processing unit is provided in a subsequent stage of the dispersion inverse function calculating means 10a, 10b or the coordinate transformation calculating means 11a to 11d, and the data series signal is an inverse function of the electro-optical conversion response characteristic of the optical modulator. Modulator inverse function calculation means 12a and 12b for correcting the amplitude are further included.

It is a block diagram which shows the structure of the transmission data series arithmetic processor of the dispersion | distribution pre-equalization optical transmitter based on Embodiment 1 of this invention. It is a block diagram which shows the structure of the optical modulator of the dispersion | distribution pre-equalization optical transmitter based on Embodiment 1 of this invention. It is a block diagram which shows the structure of the transmission data series arithmetic processor of the dispersion | distribution pre-equalization optical transmitter based on Embodiment 2 of this invention. It is a block diagram which shows the structure of the transmission data series arithmetic processor of the dispersion | distribution pre-equalization optical transmitter based on Embodiment 3 of this invention. It is a block diagram which shows the structure of the transmission data series arithmetic processor of the conventional dispersion | distribution pre-equalization optical transmitter. It is a block diagram which shows the structure of the optical modulator of the conventional dispersion | distribution pre-equalization optical transmitter.

Explanation of symbols

10, 10a, 10b Dispersion inverse function computing means 11, 11a, 11b, 11c, 11d Coordinate transformation computing means, 12a, 12b Modulator inverse function computing means, 13a, 13b D / A converter, 14a, 14b Amplifier, 20a, 20b MZ type optical modulation unit, 21 optical phase adjustment unit, 22a, 22b, 22c DC bias control unit, 23 optical demultiplexing unit, 24 optical multiplexing unit, 31, 31a, 31b branching unit, 32, 32a, 32b real part calculation Means, 33, 33a, 33b Imaginary part arithmetic means, 41, 41a, 41b Addition means.

Claims (14)

A transmission data sequence arithmetic processor for generating two series of data of I channel and Q channel;
The first optical modulation unit is driven using I-channel data of the two series of data, and the second optical modulation unit is driven using Q-channel data. A dispersion pre-equalization optical transmitter comprising: an optical modulator that transmits an optical signal that has been subjected to dispersion pre-equalization, in which an optical phase adjustment unit has an orthogonal relationship with two modulated optical signals from the modulation unit;
The transmission data series arithmetic processor is:
Dispersion inverse function computing means for performing inverse function computation of the wavelength dispersion of the transmission path and inverse function computation of the optical modulator transfer function with respect to the input transmission sequence original data,
Coordinate conversion calculation means for performing coordinate rotation of a predetermined angle with respect to the complex data obtained from the variance inverse function calculation means,
A dispersion pre-equalized optical transmitter characterized in that two series of data of I channel and Q channel are generated based on the coordinate transformed data from the coordinate transformation computing means. The distributed inverse function calculation means includes:
Real part computing means for computing only the real part of the inverse function computation on one of the same two transmission sequence original data inputted;
2. The distributed pre-equalization optical transmitter according to claim 1, further comprising: an imaginary part computing unit that performs computation of only the imaginary part of the inverse function computation on the other of the same input two transmission series original data. . The transmission data series arithmetic processor is:
The branch further includes branching means for branching the input transmission sequence source data into the same two transmission sequence source data and outputting them to the real part computing means and the imaginary part computing means, respectively. 2. The distributed pre-equalized optical transmitter according to 2. The dispersion pre-equalized optical transmitter according to claim 1, 2 or 3, wherein the coordinate transformation calculation means performs coordinate rotation of π / 4. The inverse dispersion function calculation means performs an inverse function calculation by a convolution calculation of an inverse function of a real part and an imaginary part of a transfer function of wavelength dispersion of a transmission line and the transmission sequence original data. The dispersion pre-equalization optical transmitter according to claim 4. The transmission data series arithmetic processor is:
Further provided is a modulator inverse function calculation means provided at a subsequent stage of the dispersion inverse function calculation means or the coordinate conversion calculation means and for correcting the signal amplitude of the data series with an inverse function of the response characteristic of electro-optical conversion of the optical modulator. The dispersion pre-equalized optical transmitter according to any one of claims 1 to 5, characterized in that: A transmission data sequence arithmetic processor for generating two series of data of I channel and Q channel;
The first optical modulation unit is driven using I-channel data of the two series of data, and the second optical modulation unit is driven using Q-channel data. A dispersion pre-equalization optical transmitter comprising: an optical modulator that transmits an optical signal that has been subjected to dispersion pre-equalization, in which an optical phase adjustment unit has an orthogonal relationship with two modulated optical signals from the modulation unit;
The transmission data series arithmetic processor is:
First dispersion inverse function computing means for performing inverse function computation of the chromatic dispersion of the transmission line and inverse function computation of the optical modulator transfer function with respect to the input first transmission sequence original data;
First coordinate transformation calculation means for performing coordinate rotation of a predetermined angle with respect to the complex data obtained from the first distributed inverse function calculation means;
A second dispersion inverse function computing means for performing an inverse function computation of the chromatic dispersion of the transmission line and an inverse function computation of the optical modulator transfer function with respect to the input second transmission sequence original data;
Second coordinate transformation calculation means for performing coordinate rotation of a predetermined angle on the complex data obtained from the second distributed inverse function calculation means;
First addition means for adding I channel components from the first and second coordinate transformation calculation means;
And at least second addition means for adding the Q channel components from the first and second coordinate transformation calculation means,
A dispersion pre-equalized optical transmitter characterized in that two series of data of I channel and Q channel are generated based on data from the first and second adding means. 8. The distributed pre-equalized optical transmitter according to claim 7, wherein the first and second transmission sequence original data are different data sequences to which precoding for DQPSK modulation is applied. The distributed pre-equalized optical transmitter according to claim 7, wherein the first and second transmission sequence original data are the same data sequence. The dispersion pre-equalized optical transmitter according to claim 7, 8 or 9, wherein the first and second coordinate transformation calculation means perform coordinate rotation of π / 4. The first dispersion inverse function calculation means performs an inverse function calculation by a convolution calculation of the inverse function of the real part and the imaginary part of the transmission function of the chromatic dispersion of the transmission line and the first transmission sequence original data,
The second dispersion inverse function calculation means performs an inverse function calculation by a convolution calculation of the inverse function of the real part and the imaginary part of the transfer function of the chromatic dispersion of the transmission line and the second transmission sequence original data. The dispersion pre-equalized optical transmitter according to any one of claims 7 to 10. The transmission data series arithmetic processor is:
The first dispersion inverse function calculating means or the first coordinate transformation calculating means is provided after the first, and corrects the signal amplitude of the data series with the inverse function of the electro-optical conversion response characteristic of the optical modulator. Modulator inverse function computing means;
A second dispersion inverse function computing means or a second coordinate transformation computing means, which is provided at a subsequent stage, and corrects the signal amplitude of the data series by an inverse function of the response characteristic of electro-optic conversion of the optical modulator. The dispersion pre-equalized optical transmitter according to any one of claims 7 to 11, further comprising a modulator inverse function calculation unit. The optical phase adjustment unit performs a π / 2 phase shift so that the modulated optical signal in the I channel and the modulated optical signal in the Q channel are orthogonal to each other from the two series of data of the I channel and the Q channel. The dispersion pre-equalized optical transmitter according to any one of claims 1 to 12, wherein a complex optical electric field is generated. The dispersion pre-equalized optical transmitter according to any one of claims 1 to 13, wherein the first and second optical modulation units are Mach-Zehnder type optical modulation units.

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