WO2013136716A1

WO2013136716A1 - Optical phase difference/optical carrier wave frequency difference compensation device and optical phase difference/optical carrier wave frequency difference compensation method

Info

Publication number: WO2013136716A1
Application number: PCT/JP2013/001362
Authority: WO
Inventors: 慎介藤澤; 大作小笠原; 清福知
Original assignee: 日本電気株式会社
Priority date: 2012-03-14
Filing date: 2013-03-05
Publication date: 2013-09-19

Abstract

In a multicarrier optical communications system adopting both an optical phase modulation method and a multicarrier transmission method, device configuration becomes complicated and power consumption increases. Therefore, this optical phase difference/optical carrier wave frequency difference compensation device has: a separation unit; a first optical carrier wave frequency difference compensation unit; a second optical carrier wave frequency difference compensation unit; and an optical subcarrier wave frequency interval compensation unit that connects to the first optical carrier wave frequency difference compensation unit and the second optical carrier wave frequency difference compensation unit. The separation unit receives frequency division multiplexed signals obtained by mixing frequency division multiplexed signal light with local light and performing coherent detection, said frequency division multiplexed signal light modulating and multiplexing each of a plurality of optical subcarrier waves, which have different frequencies and include at least a first optical subcarrier wave and a second optical subcarrier wave; and outputs at least a first auxiliary carrier wave signal and a second subcarrier wave signal. The first optical carrier wave frequency difference compensation unit inputs the first subcarrier wave signal and comprises: an optical phase difference detection unit that detects the amount of optical phase variation, being the amount of variation in the optical phase difference between adjacent modulation signals in the first subcarrier wave signal; and a first compensation unit that compensates the optical carrier wave frequency difference in the first subcarrier wave signal, using first optical phase difference information on the basis of the amount of optical phase variation. The optical subcarrier wave frequency interval compensation unit calculates a frequency interval compensation amount that compensates the optical subcarrier wave frequency interval being the frequency difference between the first optical subcarrier wave and the second optical subcarrier wave. The second optical carrier wave frequency difference compensation unit inputs the second subcarrier wave signal and comprises a second compensation unit that compensates the optical carrier wave frequency difference in the second subcarrier wave signal, using second optical phase difference information calculated from the frequency interval compensation amount and the first optical phase difference information.

Description

Optical phase deviation / optical carrier frequency deviation compensation apparatus and optical phase deviation / optical carrier frequency deviation compensation method

The present invention relates to an optical phase deviation / optical carrier frequency deviation compensation device and an optical phase deviation / optical carrier frequency deviation compensation method, and more particularly to an optical phase deviation / optical carrier frequency used in a division multiplexing optical communication system in which optical subcarriers are multiplexed. The present invention relates to a deviation compensator and an optical phase deviation / optical carrier frequency deviation compensation method.

With the spread of the Internet, the traffic volume of the backbone communication system is rapidly increasing. Therefore, the practical application of an ultra-high-speed optical communication system exceeding 100 Gbps (Giga bit per second) is expected. As technologies for realizing such an ultra-high-speed and large-capacity optical communication system, attention is paid to an optical phase modulation method using digital signal processing technology and a multi-carrier transmission method in which optical subcarriers are multiplexed.

The optical phase modulation method does not perform data modulation only on the light intensity of continuous wave (Continuous Wave: CW) light on the transmission side like the light intensity modulation method conventionally used, but on the transmission side CW light. This is a method for performing data modulation on the optical phase of the optical signal. As the optical phase modulation method, BPSK (2 phase shift keying: Binary Phase Shift Keying) method, QPSK (4 phase shift keying: Quadrature Phase Shift Keying) method, 8PSK (8 phase shift keying: 8-Phase Shifting) ) Method, QAM (Quadrature Amplitude Modulation) method, and the like are known. According to the optical phase modulation method, the symbol rate can be reduced by assigning a plurality of bits to one symbol. Thereby, the operation speed of the electric device can be reduced, and the manufacturing cost of the apparatus can be reduced. Here, the symbol rate has the same meaning as the baud rate, and is a value obtained by dividing the transmission bit rate by the number of bits of the modulation code. Furthermore, the optical phase modulation method is effective for increasing the number of multiplexing because the dedicated band per wave in the optical fiber can be suppressed when transmitting signal light of the same bit rate.

When the QPSK method is used, 2 bits (for example, “00”, “01”, “11”, “10” for four types of optical phases (for example, 45 degrees, 135 degrees, 225 degrees, and 315 degrees), respectively. )). At this time, since 2 bits can be allocated to one type of optical phase, the symbol rate in the QPSK method is reduced to ½ of the symbol rate (that is, the bit rate) of the binary modulation method in the light intensity modulation method. Is possible.

FIG. 11 is a diagram showing four symbols of the QPSK system and a bit string assigned thereto on the phase plane, which is called a QPSK constellation. Also, associating a bit string with each symbol in the optical phase modulation method is called symbol mapping. Hereinafter, a case where the QPSK method is used as the optical phase modulation method will be described, but the present invention can also be applied to other optical phase modulation methods.

An optical coherent method is used to receive optical phase-modulated signal light. That is, CW light (referred to as local light or local light) having substantially the same optical frequency as signal light and signal light are mixed by an optical element called 90-degree hybrid, and the output is received by a photodetector. In the following, for the sake of simplicity, it is assumed that the polarization states of the signal light and the local light are the same linearly polarized light.

When the optical coherent method is used, the AC component of the electrical signal output from the photodetector becomes a beat signal by mixing signal light and local light. The amplitude of the beat signal is proportional to the light intensity of the signal light and the local light, and the phase is the difference between the optical phase of the signal light and the local light if the carrier frequency of the signal light and the optical frequency of the local light are the same. . At this time, the optical phase does not shift in synchronization, and the phase of the beat signal does not change if the optical phase of the first received symbol is determined. Therefore, it is possible to demodulate transmission data by converting the phase of the beat signal into a bit string using symbol mapping. That is, when the first received symbol is one of the constellations shown in FIG. 11, the subsequent received symbols have the constellation shown in FIG.

However, it is difficult to completely match the value of the carrier frequency of the signal light and the value of the optical frequency of the local light because of the frequency fluctuation of the CW light source. Furthermore, the optical phase of the local light on the reception side and the optical phase of the CW light input to the optical modulator on the transmission side do not match due to the phase noise of the CW light source. Here, the optical phase difference between the CW light and the local light input to the optical modulator on the transmission side is called an optical phase deviation, and the difference between the carrier frequency of the signal light and the optical frequency of the local light is called an optical carrier frequency deviation.

12A and 12B show constellations in the case where there is an optical phase deviation and an optical carrier frequency deviation. As shown in FIG. 12A, when there is an optical phase deviation, a signal having a constellation rotated by the optical phase deviation with respect to the constellation shown in FIG. 11 is received. Since the value of the optical phase deviation cannot be known in advance, if the symbol mapping shown in FIG. 11 is used as it is and the symbol is converted into a bit string, there arises a problem that erroneous data is demodulated.

Further, when there is an optical carrier frequency deviation, the phase of the beat signal described above is a value obtained by adding the optical phase deviation to the product of the optical carrier frequency deviation and the reception time. Therefore, as shown in FIG. 12B, a signal having a constellation in which the constellation shown in FIG. 11 rotates in time is received. At this time, since the phase of the beat signal changes with time, it is impossible to demodulate data from the phase of the beat signal using the symbol mapping shown in FIG. Therefore, in the optical phase modulation method, an optical phase deviation / optical carrier frequency deviation compensation function is required in order to prevent a received signal error accompanying rotation of the constellation due to the optical phase deviation and the optical carrier frequency deviation (for example, patents) Reference 1).

Hereinafter, an optical phase deviation / optical carrier frequency deviation compensation process widely used in the optical phase modulation method will be described.

FIG. 13 shows a configuration of a related optical carrier frequency deviation compensation unit 100 of the feedforward type. The input signal of the related optical carrier frequency deviation compensation unit 100 is branched into two, one of which is input to the optical carrier frequency deviation compensation amount estimation unit 110 and the other is input to the compensation execution unit 120.

The optical carrier frequency deviation compensation amount estimation unit 110 includes an optical carrier frequency error detection unit 111, a filter unit 112, and a phase compensation amount calculation unit 113. The optical carrier frequency error detector 111 detects a change in optical phase deviation per unit time, that is, a change in optical phase deviation between two temporally adjacent symbols (modulated signals). For the optical carrier frequency error detection unit 111, an M-multiplication algorithm (M-th Power Algorithm) is widely used (for example, see Non-Patent Document 1). Here, the change in the optical phase deviation between two adjacent symbols is equal to the product of the optical carrier angular frequency deviation and one symbol time (one symbol time is equal to the reciprocal of the symbol rate). Further, since one symbol time is constant, it can be said that the optical carrier frequency error detector 111 is a circuit for calculating the optical carrier frequency deviation.

The output of the optical carrier frequency error detection unit 111 is sent to the filter unit 112, where the noise component is removed. The output of the filter unit 112 is sent to the phase compensation amount calculation unit 113 to calculate the actual phase compensation amount, that is, the rotation amount of the constellation. Specifically, the phase compensation amount calculation unit 113 is equivalent to an integration circuit.

The compensation execution unit 120 is a complex number (represented by exp (−jφ) where φ is the phase compensation amount) that gives the reverse rotation by the phase compensation amount calculated by the optical carrier frequency deviation compensation amount estimation unit 110 and the input signal. Is calculated and output as a compensated signal.

FIG. 14 shows a configuration of a related optical phase deviation compensation unit 150 of the feedforward type. The input signal of the related optical phase deviation compensation unit 150 is branched into two, one is input to the optical phase deviation compensation amount estimation unit 160 and the other is input to the compensation execution unit 170. The optical phase deviation compensation amount estimation unit 160 includes a phase error detection unit 161 and a filter unit 162. The phase error detector 161 is a circuit that detects the optical phase deviation of the input signal, and the above-mentioned M-multiplication algorithm is widely used. The output signal of the phase error detection unit 161 is sent to the filter unit 162, where the noise component is removed. The compensation execution unit 170 calculates a product of a complex number that gives reverse rotation by the amount of phase compensation based on the output signal of the filter unit 162 and the input signal, and outputs the product as a compensated signal.

As described above, in the related optical communication system using the optical phase modulation method, the optical phase deviation / optical carrier frequency deviation compensation unit shown in FIGS. 13 and 14 is used to generate the rotation of the constellation. By preventing errors in received data, the transmitted data is correctly demodulated.

Next, the multi-carrier transmission method, which is another technique for realizing an ultra-high speed and large capacity optical communication system, will be described. In the multi-carrier transmission scheme, transmission capacity can be increased by transmitting transmission data using a plurality of optical carriers (carriers) (see, for example, Patent Document 2).

As one of the multi-carrier transmission systems, a wavelength division multiplexing (WDM) is widely used. In the WDM system, a plurality of optical carriers whose frequency intervals between adjacent optical carriers are Δf are modulated with independent transmission data, and then combined to generate a transmission signal. FIG. 15A shows a frequency spectrum of an optical signal by the WDM system. As shown in the figure, in order to prevent crosstalk from adjacent optical signals, the value Δf is set to a value larger than one optical signal exclusive band. Further, by using a narrow band optical filter or the like, one optical signal dedicated band can be narrowed, and as a result, the value of Δf can be made smaller than twice the baud rate.

As another example of the multicarrier transmission system, an optical OFDM transmission system in which an orthogonal frequency division multiplexing (OFDM) system used in wireless communication is applied to optical communication has attracted attention. As a method of generating a transmission signal (optical OFDM signal) in an optical OFDM transmission system, a method of generating a transmission side CW light by using an OFDM electrical signal generated by digital signal processing on the transmission side as a modulation signal is known. Yes. In addition, an optical OFDM signal can be generated by combining a plurality of optical carriers whose frequency intervals between adjacent optical carriers are the same as the baud rate of the modulated signal after modulation with independent transmission signals.

According to the optical OFDM method, only desired optical subcarriers are separated without being affected by crosstalk from adjacent optical subcarriers (optical subcarriers) by using digital signal processing utilizing orthogonal relationships. It is possible. This is because even if the frequency spectra between adjacent optical subcarriers are partially overlapped, the frequency interval Δf between adjacent optical subcarriers is the same as the baud rate value of each optical subcarrier. This is because orthogonality is established between the carriers.

FIG. 15B shows the frequency spectrum of the optical OFDM signal. As shown in the figure, the frequency interval Δf between adjacent optical subcarriers can be reduced to the signal baud rate. Therefore, according to the optical OFDM method, the bit rate (frequency utilization efficiency) per unit frequency can be improved as compared with the wavelength division multiplexing method described above.

JP 2009-135930 A (paragraphs “0023” to “0025”) International Publication No. 2009/104758 (paragraphs “0036” to “0067”)

An optical communication system (hereinafter referred to as a multicarrier optical communication system) to which both the optical phase modulation method and the multi-carrier transmission method based on the optical OFDM transmission method are applied will be described. In the following, for the sake of simplicity, the optical OFDM signal is composed of two optical subcarrier signals (first optical subcarrier signal and second optical subcarrier signal) having the frequency spectrum shown in FIG. 15C. And

Even in a multi-carrier optical communication system, it is necessary to compensate for an optical phase deviation and an optical carrier frequency deviation in an optical OFDM signal. FIG. 16 shows the configuration of a related optical phase deviation / optical carrier frequency deviation compensator 9000 used for this purpose. The related optical phase deviation / optical carrier frequency deviation compensator 9000 is of a feed-forward type, and separates optical subcarriers obtained by orthogonal frequency division multiplexing into independent optical signals (optical subcarrier separation processing), and optical carrier frequency. A process for compensating for the deviation and the optical phase deviation is performed.

The signal data input to the optical receiver is input to the optical subcarrier separation circuit 9010 and separated into signal data corresponding to two independent optical signals. In the optical subcarrier separation circuit 9010, fast Fourier transform (FFT) processing is widely used. As described above, the optical carrier frequency deviation is generally not zero. Therefore, the signal data after separation is compensated for the rotation of the constellation due to the optical carrier frequency deviation in the optical carrier

frequency deviation compensators

9100 and 9200, respectively. Further, the optical phase deviation is compensated in the optical phase

deviation compensation units

9130 and 9230 for the signal data in which the optical carrier frequency deviation is compensated, respectively.

As described above, both the optical phase modulation method and the multicarrier transmission method are applied, and the reception side separates the optical subcarriers. Then, by compensating the optical carrier frequency deviation and the optical phase deviation for each of the two or more independent optical signals that have been separated, it is possible to realize an ultrahigh-speed optical communication system of 100 Gbps or more.

However, in the related optical phase deviation / optical carrier frequency deviation compensation device described above, the number of optical phase deviation units and optical carrier frequency deviation compensation units needs to be provided as many as the number of optical subcarriers, which complicates the configuration of the device. Power consumption will increase. As described above, in the multicarrier optical communication system to which both the optical phase modulation method and the multicarrier transmission method are applied, there is a problem that the configuration of the apparatus becomes complicated and the power consumption increases.

An object of the present invention is to solve the above-mentioned problem, that is, in a multicarrier optical communication system to which both the optical phase modulation method and the multicarrier transmission method are applied, the configuration of the apparatus becomes complicated and the power consumption increases. To provide an optical phase deviation / optical carrier frequency deviation compensation device and an optical phase deviation / optical carrier frequency deviation compensation method to be solved.

The optical phase deviation / optical carrier frequency deviation compensating apparatus of the present invention modulates and multiplexes a plurality of optical subcarriers having different frequencies including at least the first optical subcarrier and the second optical subcarrier, respectively. A demultiplexing unit that receives a frequency division multiplexed signal obtained by coherent detection by mixing with local light and outputs at least a first subcarrier signal and a second subcarrier signal; and a first subcarrier signal The first optical carrier frequency deviation compensation unit, the second optical carrier frequency deviation compensation unit to which the second subcarrier signal is inputted, the first optical carrier frequency deviation compensation unit, and the second optical carrier frequency An optical subcarrier frequency interval compensation unit connected to the deviation compensation unit, and the first optical carrier frequency deviation compensation unit is a change amount of an optical phase deviation between adjacent modulation signals in the first subcarrier signal. An optical phase deviation detecting unit for detecting a certain optical phase change amount, and a first compensating unit for compensating for an optical carrier frequency deviation in the first subcarrier signal using first optical phase deviation information based on the optical phase change amount The optical subcarrier frequency interval compensation unit calculates a frequency interval compensation amount for compensating an optical subcarrier frequency interval that is a frequency difference between the first optical subcarrier and the second optical subcarrier, The carrier frequency deviation compensator compensates for the optical carrier frequency deviation in the second subcarrier signal using the second optical phase deviation information calculated from the frequency interval compensation amount and the first optical phase deviation information. The compensation part is provided.

The optical phase deviation / optical carrier frequency deviation compensation method of the present invention is a frequency division multiplexed signal light obtained by modulating and multiplexing a plurality of optical subcarriers having different frequencies including at least the first optical subcarrier and the second optical subcarrier. Are mixed with local light to receive a frequency division multiplexed signal obtained by coherent detection, output at least a first subcarrier signal and a second subcarrier signal, and are adjacent to each other in the first subcarrier signal An optical phase change amount which is a change amount of the optical phase deviation between the modulation signals is detected, and the optical carrier frequency deviation in the first subcarrier signal is compensated using the first optical phase deviation information based on the optical phase change amount. Calculating a frequency interval compensation amount for compensating an optical subcarrier frequency interval, which is a frequency difference between the first optical subcarrier and the second optical subcarrier, and calculating from the frequency interval compensation amount and the first optical phase deviation information. To compensate for the optical carrier frequency deviation of the second sub-carrier signal using the second optical phase difference information.

According to the optical phase deviation / optical carrier frequency deviation compensation device of the present invention, even when used in a multicarrier optical communication system to which both the optical phase modulation method and the multicarrier transmission method are applied, the configuration of the device is complicated and High-speed compensation processing can be performed without causing an increase in power consumption.

1 is a block diagram showing a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus according to a first embodiment of the present invention. It is a block diagram which shows another structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 4th Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 5th Embodiment of this invention. It is a block diagram which shows a part of structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 5th Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 6th Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 7th Embodiment of this invention. It is a block diagram which shows the structure of the optical phase deviation and optical carrier frequency deviation compensation apparatus which concerns on the 8th Embodiment of this invention. It is a figure which shows an example of the constellation of QPSK and symbol mapping. It is a figure which shows an example of the constellation of QPSK and symbol mapping in case an optical phase deviation exists. It is a figure which shows an example of the constellation of QPSK and symbol mapping in case an optical carrier frequency deviation exists. It is a block diagram which shows the structure of the related feedforward type | mold optical carrier frequency deviation compensation part. It is a block diagram which shows the structure of the related feedforward type optical phase deviation compensation part. It is a figure which shows the optical frequency spectrum of the subcarrier in a multicarrier transmission system, and shows the case in a WDM system. It is a figure which shows the optical frequency spectrum of the subcarrier in a multicarrier transmission system, and shows the case by an optical OFDM system. It is a figure which shows the optical frequency spectrum of the subcarrier in a multicarrier transmission system, and shows the case by an optical OFDM system. It is a block diagram which shows the structure of the related optical phase deviation and optical carrier frequency deviation compensation apparatus. It is a block diagram which shows another structure of the related optical phase deviation and optical carrier frequency deviation compensation apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 1000 according to the first embodiment of the present invention. The optical phase deviation / optical carrier frequency deviation compensation apparatus 1000 includes a separation unit 1010, a first optical carrier frequency deviation compensation unit 1100, a second optical carrier frequency deviation compensation unit 1200, and an optical subcarrier frequency interval compensation unit 1300. .

Separating section 1010 performs coherent detection by mixing frequency division multiplexed signal light, which is obtained by modulating and multiplexing a plurality of optical subcarriers having different frequencies including at least a first optical subcarrier and a second optical subcarrier, with local light. The frequency division multiplexed signal obtained by doing so is received. The frequency division multiplexed signal is output after being separated into at least a first subcarrier signal and a second subcarrier signal.

The first optical carrier frequency deviation compensating unit 1100 receives the first subcarrier signal. The first optical carrier frequency deviation compensation unit includes an optical phase deviation detection unit 1110 and a first compensation unit 1120. The optical phase deviation detector 1110 detects an optical phase change amount that is a change amount of an optical phase deviation between adjacent modulation signals in the first subcarrier signal. The first compensation unit 1120 compensates for the optical carrier frequency deviation in the first subcarrier signal using the first optical phase deviation information based on the optical phase change amount.

The optical subcarrier frequency interval compensation unit 1300 is connected to the first optical carrier frequency deviation compensation unit 1100 and the second optical carrier frequency deviation compensation unit 1200. The optical subcarrier frequency interval compensation unit 1300 compensates for an optical subcarrier frequency interval that is a frequency difference between the first optical subcarrier and the second optical subcarrier.

The second optical carrier frequency deviation compensation unit 1200 includes a second compensation unit 1220 and inputs a second subcarrier signal. The second compensation unit 1220 compensates the optical carrier frequency deviation in the second subcarrier signal using the second optical phase deviation information calculated from the frequency interval compensation amount and the first optical phase deviation information.

In the optical phase deviation / optical carrier frequency deviation compensation device, a first subcarrier signal (subcarrier signal) which is one of frequency division multiplexed signals obtained from a plurality of optical subcarriers (also referred to as “optical subcarriers”). ) To detect the optical phase change amount. Based on the optical phase change amount and the optical subcarrier frequency interval, the optical phase deviation and the optical carrier frequency deviation in all the optical subcarriers (optical subcarriers) are compensated. Therefore, the optical phase deviation detector that detects the optical phase change amount can cope with one even when receiving a plurality of optical subcarriers (optical subcarriers).

As described above, according to the optical phase deviation / optical carrier frequency deviation compensation apparatus 1000 of the present embodiment, even when used in a multicarrier optical communication system, the configuration of the apparatus is not complicated and the power consumption is not increased. High-speed compensation processing can be performed.

As shown in FIG. 2, the optical phase deviation / optical carrier frequency deviation compensation apparatus 1000 includes a first optical phase deviation compensation unit 1410 on the path of the first subcarrier signal and a path of the second subcarrier signal. The second optical phase deviation compensation unit 1420 can be further provided.

Here, the first optical phase deviation compensation unit 1410 calculates the optical phase deviation compensation amount estimation unit 1411 for calculating the optical phase deviation compensation amount, and calculates the optical phase deviation in the first subcarrier signal based on the optical phase deviation compensation amount. A first phase compensation unit 1412 for compensation is provided. The second optical phase deviation compensation unit 1420 includes a second phase compensation unit 1422. The second phase compensator 1422 is based on the value obtained by adding the optical phase deviation compensation amount to the phase deviation between the first optical subcarrier and the second optical subcarrier, and the optical signal in the second subcarrier signal. Compensate for phase deviation.

Next, compensation for optical phase deviation will be described in more detail. As shown in FIG. 2, the optical phase deviation / optical carrier frequency deviation compensation apparatus 1000 according to the present embodiment uses all the optical phase deviation compensation amounts in one optical subcarrier (optical subcarrier) (2 in the case of FIG. 2). This is commonly used for optical phase deviation compensation in optical subcarriers. That is, the optical phase deviation compensation amount estimation unit 1411 is provided only in one of the plurality of optical phase deviation compensation units (the first optical phase deviation compensation unit 1410 in FIG. 2). Then, the second phase compensation unit 1422 compensates for the optical phase deviation in the second subcarrier signal based on the value obtained by adding the optical phase deviation compensation amount to the phase deviation between the two optical subcarriers.

Since the independent signal data input to the first optical phase deviation compensation unit 1410 and the second optical phase deviation compensation unit 1420 are received at the same time, the phase deviation is the same. Therefore, the optical phase deviation compensation amount estimated by the optical phase deviation compensation amount estimation unit of one optical phase deviation compensation unit can be applied to the signal data of the other optical phase deviation compensation unit. Therefore, according to the present embodiment, it is possible to have a configuration including only one optical phase deviation compensation amount estimation unit.

Note that there may be a difference in the amount of optical phase deviation compensation between two independent signal data due to a skew between the two independent optical signals. Even in this case, the time variation of the optical phase deviation compensation amount difference Δθ is small. Therefore, if Δθ is known, second phase compensation section 1422 can compensate for the optical phase deviation in the second subcarrier signal based on a value obtained by further adding Δθ.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 2000 according to the second embodiment of the present invention. The optical phase deviation / optical carrier frequency deviation compensation apparatus 2000 includes an optical subcarrier separation circuit 2010 as a separation unit, a first optical carrier frequency deviation compensation unit 2100, a second optical carrier frequency deviation compensation unit 2200, and an optical subcarrier. An optical subcarrier frequency interval calculation unit 2300 is provided as a frequency interval compensation unit. FIG. 3 shows a configuration in which the optical phase deviation compensation unit 150 is provided in the subsequent stage of the first optical carrier frequency deviation compensation unit 2100 and the second optical carrier frequency deviation compensation unit 2200. The configuration and operation have been described with reference to FIG.

The first optical carrier frequency deviation compensation unit 2100 includes a first optical carrier frequency deviation compensation amount estimation unit 2110 and a first compensation execution unit 2120. The first optical carrier frequency deviation compensation amount estimation unit 2110 includes an optical carrier frequency error detection unit 2111, a filter unit 2112, and a first phase compensation amount calculation unit 2113. Here, the optical carrier frequency error detection unit 2111 and the filter unit 2112 constitute an optical phase deviation detection unit, and the amount of change in optical phase deviation between adjacent modulation signals in the first subcarrier signal (subcarrier 1 signal). A certain amount of optical phase change is detected.

The first phase compensation amount calculation unit 2113 calculates the first phase compensation amount by time-integrating the optical phase change amount as the first optical phase deviation information. The first compensation execution unit 2120 as the first compensation unit compensates for the optical carrier frequency deviation in the first subcarrier signal using the first phase compensation amount.

The optical subcarrier frequency interval calculator 2300 as the optical subcarrier frequency interval compensator acquires the optical phase change amount as the first optical phase deviation information from the first optical carrier frequency deviation compensator 2100. Then, a value proportional to the product of the optical subcarrier frequency interval (optical subcarrier frequency interval Δf) and the time interval (symbol time) between adjacent modulation signals is added to the optical phase change amount as a frequency interval compensation amount. Second optical phase deviation information is calculated. Thereafter, the second optical phase deviation information is sent to the second optical carrier frequency deviation compensator 2200.

The second optical carrier frequency deviation compensation unit 2200 includes a second optical carrier frequency deviation compensation amount estimation unit 2210 including a second phase compensation amount calculation unit 2213, and a second compensation execution unit 2220. The second phase compensation amount calculation unit 2213 calculates the second phase compensation amount by time-integrating the second optical phase deviation information. The second compensation execution unit 2220 as the second compensation unit compensates for the optical carrier frequency deviation in the second subcarrier signal (subcarrier 2 signal) using the second phase compensation amount.

Next, the configuration of the optical phase deviation / optical carrier frequency deviation compensating apparatus 2000 of this embodiment will be described in more detail. In the following description, for simplicity, an optical OFDM signal composed of two optical subcarriers (hereinafter referred to as “optical subcarriers”) having the frequency spectrum shown in FIG. 15C is used as the frequency division multiplexed signal. The case will be described. In the figure, “Δf” represents the frequency interval between adjacent optical subcarriers, and the value of Δf is the same as the baud rate value of each subcarrier.

As shown in FIG. 3, the input signal is separated into two subcarriers by processing such as FFT in an optical subcarrier separation circuit 2010. One output signal of the optical subcarrier separation circuit 2010 is sent to the first optical carrier frequency deviation compensation unit 2100, and the other output signal is inputted to the second optical carrier frequency deviation compensation unit 2200.

The input signal of the first optical carrier frequency deviation compensation unit 2100 is branched into two, one is input to the first optical carrier frequency deviation compensation amount estimation unit 2110 and the other is input to the first compensation execution unit 2120. The The first optical carrier frequency deviation compensation amount estimation unit 2110 includes an optical carrier frequency error detection unit 2111, a filter unit 2112, and a first phase compensation amount calculation unit 2113. The output signal of the filter unit 2112 is sent to the optical subcarrier frequency interval calculation unit 2300.

The input signal of the second optical carrier frequency deviation compensation unit 2200 is input to the second compensation execution unit 2220. In second optical carrier frequency deviation compensation amount estimation unit 2210, the output signal from optical subcarrier frequency interval calculation unit 2300 is input to second phase compensation amount calculation unit 2213. The phase compensation amount calculated by the second phase compensation amount calculation unit 2213 is sent to the second compensation execution unit 2220, and the second compensation execution unit 2220 compensates for the optical carrier frequency deviation in the optical subcarrier 2 signal.

The optical phase deviation / optical carrier frequency deviation compensator 2000 according to the present embodiment has one of the first optical carrier frequency deviation compensation unit 2100 and the second optical carrier frequency deviation compensation unit 2200 (the first optical carrier in FIG. Only the carrier frequency deviation compensating unit 2100) includes an optical carrier frequency error detecting unit 2111 and a filter unit 2112. The optical subcarrier frequency interval calculation unit 2300 then adds the value obtained by multiplying the optical subcarrier frequency interval Δf by 2π times the symbol time of the received optical signal to the output signal of the filter unit 2112, This is supplied to the phase compensation amount calculation unit 2213.

Next, the operation of the optical phase deviation / optical carrier frequency deviation compensating apparatus 2000 of this embodiment will be described. In FIG. 15C, the optical subcarrier frequency interval of the optical OFDM signal is Δf, the average optical carrier frequency f _{0 of} the optical OFDM signal (hereinafter referred to as “subcarrier center optical frequency”), and the optical frequency f _{LO of the} local light. The optical frequency deviation during the period is Δf _LO . From the figure, the optical carrier frequency deviation in subcarrier 1 is Δf / 2 + Δf _LO , whereas the optical carrier frequency deviation in subcarrier 2 is Δf / 2−Δf _LO . Here, since the optical subcarrier frequency interval Δf is known, the optical frequency deviation Δf _LO in one type of subcarrier calculated in one optical carrier frequency deviation compensation amount estimation unit is used, and the light in all subcarriers is detected. It becomes possible to compensate for the frequency deviation.

In addition, independent signal data input to the first optical carrier frequency deviation compensation unit 2100 and the second optical carrier frequency deviation compensation unit 2200 are received at the same time. Thus, a value obtained by multiplying the frequency deviation estimated by the optical carrier frequency deviation compensation amount estimation unit provided in one optical carrier frequency deviation compensation unit by the value of 2π times the symbol time of the received optical signal by the optical subcarrier frequency interval is obtained. By adding, the frequency deviation of the other optical subcarrier can be estimated.

Therefore, by applying the frequency deviation estimated from the frequency deviation of one optical subcarrier to the frequency deviation compensation amount of the other subcarrier, it is possible to reduce the phase error detection processing and filter processing of the other optical subcarrier. It becomes.

Since the symbol time of the input signal of the optical phase deviation / optical carrier frequency deviation compensation device 2000 is generally the same value as the reciprocal of the baud rate of the optical signal, it is a predetermined value determined in advance. In particular, for an optical OFDM signal, the optical subcarrier frequency interval Δf is equal to the symbol time of the received optical signal, so the added value in the optical subcarrier frequency interval calculation unit 2300 is always “2π”. Since the phase rotation corresponding to “2π” is “1”, in the case of an optical OFDM signal, the addition processing in the optical subcarrier frequency interval calculation unit 2300 can be omitted.

It should be noted that there may be a difference in the compensation amount for the optical phase deviation between the two independent signal data due to the time lag (skew) between the two independent optical signals. Even in this case, since the time variation of the optical carrier frequency deviation is small, it is possible to compensate the other optical phase deviation based on one compensation amount.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 4 is a block diagram showing a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 3000 according to the third embodiment of the present invention. The optical phase deviation / optical carrier frequency deviation compensation device 3000 includes an optical subcarrier separation circuit 2010 as a separation unit, a first optical carrier frequency deviation compensation unit 3100, a second optical carrier frequency deviation compensation unit 3200, and an optical subcarrier. An optical subcarrier frequency interval integration unit 3300 as a frequency interval compensation unit is provided.

The first optical carrier frequency deviation compensation unit 3100 includes an optical carrier frequency deviation compensation amount estimation unit 3110 including an optical phase deviation detection unit and a first phase compensation amount calculation unit, and a first compensation as a first compensation unit. An execution unit 3120 is provided. The optical carrier frequency deviation compensation amount estimation unit 3110 calculates the first phase compensation amount as the first optical phase deviation information by time-integrating the optical phase change amount. The first compensation execution unit 3120 compensates for the optical carrier frequency deviation in the first subcarrier signal using the first phase compensation amount.

The optical subcarrier frequency interval integration unit 3300 acquires the first phase compensation amount from the first optical carrier frequency deviation compensation unit 3100. Then, a value proportional to the product of the optical subcarrier frequency interval and the time interval (symbol time) between adjacent modulation signals and the number of modulation signals (number of processed symbols) is added to the first phase compensation amount as the frequency interval compensation amount. As a result, the second phase compensation amount as the second optical phase deviation information is calculated. Thereafter, the second phase compensation amount is sent to the second optical carrier frequency deviation compensating unit 3200.

The second optical carrier frequency deviation compensation unit 3200 includes a second compensation execution unit 3220 as a second compensation unit. Second compensation execution unit 3220 compensates for the optical carrier frequency deviation in the second subcarrier signal using the second phase compensation amount.

As described above, the optical subcarrier frequency interval integration unit 3300 of this embodiment is 2π times the product of the symbol time of the received optical signal and the number of processing symbols (hereinafter referred to as “elapsed time”) in the optical subcarrier frequency interval Δf. A value obtained by multiplying the values is calculated as a frequency interval compensation amount. Then, the frequency interval compensation amount is added to the first phase compensation amount output from the optical carrier frequency deviation compensation amount estimation unit 3110 and supplied to the second compensation execution unit 3220 provided in the second optical carrier frequency deviation compensation unit 3200. To do. That is, the function of the second phase compensation amount calculation unit 2213 provided in the second optical carrier frequency deviation compensation amount estimation unit 2210 in the second embodiment is provided to the optical subcarrier frequency interval integration unit 3300 in this embodiment. The configuration.

Next, the operation of the optical phase deviation / optical carrier frequency deviation compensating apparatus 3000 according to this embodiment will be described. In FIG. 15C, the optical subcarrier frequency interval of the optical OFDM signal is Δf, and the optical frequency deviation between the subcarrier center optical frequency f ₀ and the local light optical frequency f _LO is Δf _LO . From the figure, the optical carrier frequency deviation in subcarrier 1 is Δf / 2 + Δf _LO , whereas the optical carrier frequency deviation in subcarrier 2 is Δf / 2−Δf _LO . Here, since the optical subcarrier frequency interval Δf is known, the optical frequency deviation Δf _LO in one type of subcarrier calculated in one optical carrier frequency deviation compensation amount estimation unit is used, and the light in all subcarriers is detected. It becomes possible to compensate for the frequency deviation.

Further, independent signal data input to the first optical carrier frequency deviation compensation unit 3100 and the second optical carrier frequency deviation compensation unit 3200 are received at the same time. Thus, the value obtained by multiplying the optical subcarrier frequency interval Δf by 2π times the elapsed time is added to the frequency deviation estimated by the optical carrier frequency deviation compensation amount estimation unit provided in one of the optical carrier frequency deviation compensation units. Thus, the frequency deviation of the other optical subcarrier can be estimated.

Therefore, by applying the frequency deviation estimated from the frequency deviation of one optical subcarrier to the frequency deviation compensation amount of the other subcarrier, the phase error detection processing of the other optical subcarrier can be reduced.

Here, for an optical OFDM signal, the optical subcarrier frequency interval Δf is equal to the symbol time of the received optical signal. Therefore, a value obtained by multiplying the optical subcarrier frequency interval Δf by a value 2π times the elapsed time is an integral multiple of “2π”. Since the phase rotation corresponding to an integral multiple of “2π” is “1”, in the case of an optical OFDM signal, the process of adding the frequency interval compensation amount in the optical subcarrier frequency interval integrating unit 3300 can be omitted.

Even when there is a skew between two independent signal data, the time variation of the optical carrier frequency deviation is small, so that it is possible to compensate the other optical phase deviation based on one compensation amount. It is.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 5 is a block diagram showing a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 4000 according to the fourth embodiment of the present invention. The optical phase deviation / optical carrier frequency deviation compensation device 4000 includes an optical subcarrier separation circuit 2010 as a separation unit, a first optical carrier frequency deviation compensation unit 3100, and a second optical carrier frequency deviation compensation unit 3200.

The configuration so far is the same as the configuration of the optical phase deviation / optical carrier frequency deviation compensation device 3000 of the third embodiment. The optical phase deviation / optical carrier frequency deviation compensation device 4000 according to the present embodiment includes the operation of the second optical carrier frequency deviation compensation unit 3200 and the configuration of the optical subcarrier frequency interval compensation unit as the optical subcarrier frequency interval compensation unit. Different from the third embodiment.

That is, the second optical carrier frequency deviation compensation unit 3200 includes a second compensation execution unit 3220 as a second compensation unit. The second compensation execution unit 3220 compensates for the optical carrier frequency deviation in the second subcarrier signal by using the first phase compensation amount as the second optical phase deviation information.

The optical subcarrier frequency interval compensation unit includes a first optical subcarrier frequency interval compensation unit 4310 serving as a first optical subcarrier frequency interval compensation unit and a second optical subcarrier frequency interval compensation unit serving as a second optical subcarrier frequency interval compensation unit. The optical subcarrier frequency interval compensation unit 4320 of FIG.

Here, the first optical subcarrier frequency interval compensation unit 4310 is connected to the first optical carrier frequency deviation compensation unit 3100, and calculates the difference between the average frequency of the plurality of optical subcarriers and the frequency of the first optical subcarrier. A first frequency interval compensation amount to be compensated is given. On the other hand, the second optical subcarrier frequency interval compensation unit 4320 is connected to the second optical carrier frequency deviation compensation unit 3200 to compensate for the difference between the average frequency of the plurality of optical subcarriers and the frequency of the second optical subcarrier. A second frequency interval compensation amount is given.

Specifically, as shown in FIG. 5, the first optical subcarrier frequency interval compensation unit 4310 rotates the phase of subcarrier 1 by a value obtained by multiplying “Δf / 2” by 2π times the elapsed time. give. On the other hand, second optical subcarrier frequency interval compensation unit 4320 gives phase rotation to subcarrier 2 by a value obtained by multiplying “−Δf / 2” by 2π times the elapsed time. This makes it possible to compensate for the optical subcarrier frequency interval.

Next, the operation of the optical phase deviation / optical carrier frequency deviation compensating apparatus 4000 of this embodiment will be described. In FIG. 15C, the optical subcarrier frequency interval of the optical OFDM signal is Δf, and the optical frequency deviation between the subcarrier center optical frequency f ₀ and the local light optical frequency f _LO is Δf _LO . Before the first and second optical carrier frequency

deviation compensation units

3100 and 3200, the first and second optical subcarrier frequency

interval compensation units

4310 and 4320 each have a frequency interval Δf between two optical subcarriers in advance. To compensate. As a result, the optical carrier frequency deviation between the two optical subcarriers is the same as Δf _LO . Here, the independent signal data respectively input to the first and second optical carrier frequency

deviation compensating units

3100 and 3200 are received at the same time. Thus, the first phase compensation amount estimated by the optical carrier frequency deviation compensation amount estimation unit 3110 included in the first optical carrier frequency deviation compensation unit 3100 is applied as it is, and the second optical carrier frequency deviation compensation unit 3200 performs sub- The frequency deviation in the carrier 2 can be compensated. As a result, according to this embodiment, the second optical carrier frequency deviation compensation unit 3200 does not require a phase compensation amount calculation unit, and the configuration of the apparatus can be simplified.

Note that an optical subcarrier frequency interval compensator must be provided for each subcarrier path. However, as shown in FIG. 5, it is not necessary to arrange the optical subcarrier frequency interval compensation unit between the optical subcarrier separation circuit 2010 and the first and second optical carrier frequency

deviation compensation units

3100 and 3200. For example, the input of the optical subcarrier separation circuit 2010 is branched into two, and one of the branches is input to the first optical subcarrier frequency interval compensation unit 4310 and the other is input to the second optical subcarrier frequency interval compensation unit 4320. It is good also as a structure. Also in this case, the two signals obtained by performing the optical subcarrier separation processing using the output signals of the first and second optical subcarrier frequency

interval compensation units

4310 and 4320 as input signals are shown in FIG. It becomes the same as the output signal in the configuration shown in FIG.

Specifically, the signal data transmitted from the first optical subcarrier frequency interval compensation unit 4310 to the optical subcarrier separation circuit 2010 is subjected to FFT calculation in the optical subcarrier separation circuit 2010. Thereafter, only one of the output signals of the optical subcarrier separation circuit 2010 is input to the first optical carrier frequency deviation compensation unit 3100. Similarly, the signal data transmitted from the second optical subcarrier frequency interval compensation unit 4320 to the optical subcarrier separation circuit 2010 is subjected to FFT calculation in the optical subcarrier separation circuit 2010. Then, only one of the output signals of the optical subcarrier separation circuit 2010 can be input to the second optical carrier frequency compensation unit 3200.

When the configuration shown in FIG. 5, that is, when the optical subcarrier frequency

interval compensation units

4310 and 4320 are arranged between the optical subcarrier separation circuit 2010 and the optical carrier frequency

deviation compensation units

3100 and 3200, the optical carrier frequency deviation compensation unit is provided. Can be narrowed. This is because the optical carrier frequency deviation of the input signal of the optical carrier frequency deviation compensation unit is small.

As in the second and third embodiments, even if there is a skew between two independent signal data, the other optical phase deviation is compensated based on one compensation amount. can do.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. In the present embodiment, a case where a polarization multiplexing / demultiplexing technique is used will be described. As a technique for realizing a large-capacity optical communication system, a polarization multiplexing / demultiplexing technique is known in addition to the optical phase modulation method and the multicarrier transmission method described above. The polarization multiplexing / demultiplexing technology multiplexes two kinds of independent optical signals whose carrier waves belong to the same frequency band and whose polarization states are orthogonal to each other in the optical transmitter, and receives the above two kinds from the received signal in the optical receiver. It is a technology that separates the optical signal. Thereby, a double transmission speed can be realized.

FIG. 17 shows an optical receiver used in an optical communication system (hereinafter referred to as “multicarrier polarization multiplexed optical communication system”) employing an optical phase modulation method, a multicarrier transmission method, and a polarization multiplexing / demultiplexing technique. The configuration of a related optical phase deviation / optical carrier frequency deviation compensating apparatus 9500 is shown. The signal data input to the optical receiver is separated into two subcarrier signals by the optical subcarrier separation circuit 9010 and is input to the polarization separation unit 9510 and the polarization separation unit 9520 for each subcarrier. In the

polarization separators

9510 and 9520, each subcarrier is further separated into signal data corresponding to two independent optical signals, and the optical phase deviation and carrier frequency deviation are compensated for a total of four independent signal data. Is done. Here, CMA (Constant Modulus Algorithm) is widely used for signal processing in the

polarization separation units

9510 and 9520.

In this embodiment, an optical phase deviation / optical carrier frequency deviation compensation apparatus applied to the above-described multicarrier polarization multiplexed optical communication system will be described.

FIG. 6 shows the configuration of an optical phase deviation / optical carrier frequency deviation compensation device 5000 according to this embodiment. The optical phase deviation / optical carrier frequency deviation compensation device 5000 is configured by applying the optical phase deviation / optical carrier frequency deviation compensation device 2000 according to the second embodiment to a multicarrier polarization multiplexed optical communication system. A wave separation unit 5010 and a second polarization separation unit 5020 are provided. Here, the optical carrier frequency deviation between signal data belonging to mutually orthogonal polarization states is equal. From this, the compensation amount estimation value for the optical carrier frequency deviation of any one optical subcarrier in one polarization state is commonly used in consideration of the optical carrier frequency interval between the optical subcarriers. It can be used as a frequency compensation value.

That is, four optical carrier frequency deviation compensation units, that is, a first optical carrier frequency deviation compensation unit 5110, a second optical carrier frequency deviation compensation unit 5120, a third optical carrier frequency deviation compensation unit 5210, and a fourth optical carrier frequency deviation compensation unit 5210, Only one of the optical carrier frequency deviation compensation units 5220 includes the optical carrier frequency deviation compensation amount estimation unit. Here, as shown in FIG. 7, a case where only the first optical carrier frequency deviation compensation unit 5110 includes the first optical carrier frequency deviation compensation amount estimation unit 2110 will be described. Here, the configuration of the first optical carrier frequency deviation compensating unit 5110 is the same as that of the first optical carrier frequency deviation compensating unit 2100 in the second embodiment. The configurations of the second to fourth optical carrier frequency

deviation compensating units

5120, 5210, and 5220 are the same as those of the second optical carrier frequency deviation compensating unit 2200 in the second embodiment.

The first optical carrier frequency deviation compensation amount estimation unit 2110 provided in the first optical carrier frequency deviation compensation unit 5110 includes an optical carrier frequency error detection unit 2111 and a filter unit 2112, and outputs an output signal from the filter unit 2112 to the first optical carrier frequency error compensation unit 5110. This is supplied to the phase compensation amount calculation unit 2113. The optical subcarrier frequency interval calculation unit 2300 adds the value obtained by multiplying the optical subcarrier frequency interval Δf by 2π times the symbol time of the received optical signal to the output signal of the filter unit 2112. The result of the addition is supplied to two phase compensation amount calculation units for the subcarrier 2, that is, the second phase compensation amount calculation unit 2213.

In general, the symbol time of the input signal of the optical phase deviation / optical carrier frequency deviation compensation unit is the same value as the reciprocal of the baud rate of the optical signal, and is a predetermined value. In particular, for an optical OFDM signal, the value obtained by multiplying the optical subcarrier frequency interval Δf by 2π times the symbol time of the received optical signal is “2π”. Therefore, in the case of an optical OFDM signal, the addition function in the optical subcarrier frequency interval calculation unit 2300 can be omitted.

Independent signal data input to each optical carrier frequency deviation compensation unit is received at the same time. Further, the optical carrier frequencies of two independent optical signals in the polarization state that are orthogonal to each other are the same. From these, in each subcarrier, the compensation amount estimated by the optical carrier frequency deviation compensation amount estimation unit of the optical carrier frequency deviation compensation unit for one polarization state is changed to the optical carrier frequency deviation compensation unit for the other polarization state. It can be applied to signal data. Therefore, by applying the frequency deviation estimated from the frequency deviation of the optical subcarrier in one polarization state to the frequency deviation compensation amount of the optical subcarrier in the other polarization state, Phase error detection processing and filter processing can be reduced.

That is, as described in the second embodiment, there is a difference Δf in the frequency deviation estimated from the signal data belonging to each subcarrier. Therefore, a value obtained by multiplying the optical subcarrier frequency interval Δf by a value 2π times the symbol time of the received optical signal is applied to the frequency deviation compensation amount of other subcarriers. As a result, it is possible to reduce the phase error detection process and the filter process for other optical subcarriers. As described above, according to the present embodiment, a total of three optical carrier frequency error detection units 2111 and filter units 2112 can be reduced.

Note that even if there is a skew in the four independent signal data, the time variation of the optical carrier frequency deviation is small, so that other optical phase deviations can be compensated based on one compensation amount.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 8 shows a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 6000 in the present embodiment. The optical phase deviation / optical carrier frequency deviation compensator 6000 includes a first optical subcarrier frequency interval compensation unit 6310, a first polarization separation unit 6010, a second optical subcarrier frequency interval compensation unit 6320, and a second optical subcarrier frequency interval compensation unit 6310. A polarization separation unit 6020 is included.

In the first optical subcarrier frequency interval compensation unit 6310, the phase rotation is given to the subcarrier 1 by a value obtained by multiplying Δf / 2 by 2π times the elapsed time. Further, second optical subcarrier frequency interval compensation section 6320 gives phase rotation to subcarrier 2 by a value obtained by multiplying −Δf / 2 by 2π times the elapsed time.

Four optical carrier frequency deviation compensation units, that is, a first optical carrier frequency deviation compensation unit 5110, a second optical carrier frequency deviation compensation unit 5120, a third optical carrier frequency deviation compensation unit 5210, and a fourth optical carrier Only one of the frequency deviation compensation units 5220 includes an optical carrier frequency deviation compensation amount estimation unit. Here, only the first optical carrier frequency deviation compensation unit 5110 is provided with the first optical carrier frequency deviation compensation amount estimation unit 2110. Then, the compensation amount estimated by the optical carrier frequency deviation compensation amount estimation unit 2110 is supplied to each compensation amount execution unit.

As described in the fourth embodiment, independent signal data input to the first optical carrier frequency deviation compensation unit 5110 and the second optical carrier frequency deviation compensation unit 5120 are received at the same time. From this, the optical carrier frequency deviation becomes the same after the phase rotation is given by the value obtained by multiplying ± f / 2 by a value 2π times the elapsed time. Furthermore, the optical carrier frequencies of two independent optical signals in the polarization state that are orthogonal to each other are the same. Therefore, with respect to one optical subcarrier included in any one polarization state, the compensation amount estimated by the optical carrier frequency deviation compensation amount estimation unit provided in the optical carrier frequency deviation compensation unit is used as another optical carrier. It can be applied as it is to the signal data of the frequency deviation compensator. Therefore, according to this embodiment, a total of three optical carrier frequency deviation compensation amount estimation units can be reduced.

Note that one optical subcarrier frequency interval compensator is necessarily required for each subcarrier, but between the optical subcarrier separation circuit 2010, the first polarization separation unit 6010, and the second polarization separation unit 6020. There is no need to prepare for. However, when the first and second optical subcarrier frequency

interval compensation units

6310 and 6320 are provided in front of the first to fourth optical carrier frequency deviation compensation units, respectively, the input signal of the optical carrier frequency deviation compensation unit is Since the optical carrier frequency deviation is small, the frequency range of the optical carrier frequency deviation compensator can be narrowed.

Even when there is a skew between four independent signal data, the time variation of the optical carrier frequency deviation is small, so that other optical phase deviations can be compensated based on one compensation amount. .

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. FIG. 9 shows a configuration of an optical phase deviation / optical carrier frequency deviation compensating apparatus 7000 in the present embodiment. The optical phase deviation / optical carrier frequency deviation compensation device 7000 includes a first polarization separation unit 7010, a first optical phase deviation compensation unit 7410, and a second optical phase deviation compensation unit 7420 in the path of the X polarization signal. Prepare. The Y polarization signal path includes a second polarization separation unit 7020, a third optical phase deviation compensation unit 7430, and a fourth optical phase deviation compensation unit 7440. Here, only one of the first to fourth optical phase deviation compensation units (the first optical phase deviation compensation unit 7410 in FIG. 9) includes the optical phase deviation compensation amount estimation unit. Then, in the three optical phase deviation adders 7450, the optical phase deviation compensator has three values obtained by adding the phase deviation between independent signals to the compensation amount estimated by the optical phase deviation compensation amount estimator. Each phase compensation unit is configured to be supplied.

The independent signal data input to the first optical phase deviation compensation unit 7410, the second optical phase deviation compensation unit 7420, the third optical phase deviation compensation unit 7430, and the fourth optical phase deviation compensation unit 7440 are the same. Received at the time. For this reason, since the phase deviation is the same, the compensation amount estimated by the optical phase deviation compensation amount estimation unit provided in the first optical phase deviation compensation unit 7410 is changed to that of the other second to fourth optical phase deviation compensation units. It can be applied to signal data. Therefore, according to the present embodiment, three optical phase deviation compensation amount estimation units can be reduced.

Note that there may be a difference in the compensation amount for the optical phase deviation of the independent signal data due to the skew between the independent optical signals. Even in this case, by adding the difference in the compensation amount with respect to the optical phase deviation in the optical phase deviation adder 7450, the other optical phase deviation can be compensated based on the one compensation amount.

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. In the above-described embodiment, the case where an optical OFDM signal having two optical subcarriers is used has been described. However, the present invention is not limited to this, and an optical OFDM signal having three or more optical subcarriers can be similarly compensated. That is, the output signal of each optical carrier frequency deviation compensation unit for another optical subcarrier can be obtained from the signal in the optical carrier frequency deviation compensation amount estimation unit for one optical subcarrier and the optical subcarrier interval Δf. Therefore, the optical phase deviation and the optical carrier frequency deviation can be compensated for an optical OFDM signal having N optical subcarriers.

FIG. 10 shows a configuration of an optical phase deviation / optical carrier frequency deviation compensation device 8000 in the present embodiment. Of the N output signals of the optical subcarrier separation circuit 8010, the first optical carrier frequency deviation compensation unit 2100 for one optical subcarrier detects an optical carrier frequency error detection value. Then, in N−1 optical subcarrier frequency interval calculation unit 2300, a value obtained by multiplying optical subcarrier frequency interval Δf by 2π times the symbol time of the received optical signal is added to the optical carrier frequency error detection value. . The value after the addition is supplied to a second phase compensation amount calculation unit provided in each second optical carrier frequency deviation compensation unit 2200. Thereby, it becomes possible to compensate for the optical carrier frequency deviation of all the optical subcarriers based on one optical subcarrier optical carrier frequency deviation.

Next, the operation of the optical phase deviation / optical carrier frequency deviation compensator 8000 according to this embodiment will be described. As shown in FIG. 15B, the optical subcarrier interval Δf of the optical OFDM signal is constant. Further, the first optical carrier frequency deviation compensating unit 2100 can calculate an estimated value of the optical carrier frequency deviation for one subcarrier. Therefore, a value obtained by multiplying each optical subcarrier frequency interval by the symbol time is added to this estimated value, and the value after addition can be used to compensate for the optical carrier frequency deviation for all the optical subcarriers. . That is, since the frequency deviation estimated from the frequency deviation of one optical subcarrier can be applied to the frequency deviation compensation amount of all other optical subcarriers, phase error detection processing and filter processing in other optical subcarriers are possible. Can be reduced.

The symbol time of the input signal of the optical phase deviation / optical carrier frequency deviation compensation unit is generally the same value as the reciprocal of the baud rate of the optical signal, and is a predetermined value determined in advance. In particular, for an optical OFDM signal, the value obtained by multiplying the optical subcarrier frequency interval Δf by 2π times the symbol time of the received optical signal is “2π”, so the addition in the optical subcarrier frequency interval calculation unit 2300 is performed. The function can be omitted.

It should be noted that there may be a difference in the compensation amount for the optical phase deviation between the two independent signal data due to the time lag (skew) between the two independent optical signals. However, even in such a case, since the time variation of the optical carrier frequency deviation is small, other optical phase deviations can be compensated based on one compensation amount.

Further, the compensation amount estimated by the optical phase deviation compensation amount estimation unit 160 included in the optical phase deviation compensation unit 150 for any one subcarrier has the same phase deviation. It can also be applied to signal data. Therefore, according to this embodiment, the optical phase deviation compensation amount estimation unit 160 can be reduced.

In the above embodiment, the case where an optical OFDM signal is used as the multicarrier transmission system has been described as an example. However, the present invention is not limited to this, and the present invention can also be applied to other multicarrier transmission systems in which the frequency interval between adjacent optical subcarriers is a constant value.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it is also included within the scope of the present invention. Not too long.

This application claims priority based on Japanese Patent Application No. 2012-056761 filed on Mar. 14, 2012, the entire disclosure of which is incorporated herein.

1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000 Optical phase deviation / optical carrier frequency deviation compensation device 1010 Separating unit 1100, 2100, 3100, 5110 First optical carrier frequency deviation compensating unit 1110 Optical phase deviation detecting unit 1120 First compensation unit 1200, 2200, 3200, 5120 Second optical carrier frequency deviation compensation unit 1220 Second compensation unit 1300 Optical subcarrier frequency interval compensation unit 1410, 7410 First optical phase deviation compensation unit 1411 Optical phase Deviation compensation amount estimation unit 1412 First phase compensation unit 1420, 7420 Second optical phase deviation compensation unit 1422 Second phase compensation unit 2010, 8010 Optical subcarrier separation circuit 2110 First optical carrier frequency deviation compensation amount estimation unit 2111 Optical carrier frequency error detection Unit 2112 filter unit 2113 first phase compensation amount calculation unit 2120, 3120 first compensation execution unit 2210 second optical carrier frequency deviation compensation amount estimation unit 2213 second phase compensation amount calculation unit 2220, 3220 second compensation Execution unit 2300 Optical subcarrier frequency interval calculation unit 3300 Optical subcarrier frequency interval integration unit 3110 Optical carrier frequency deviation compensation amount estimation unit 4310, 6310 First optical subcarrier frequency interval compensation unit 4320, 6320 Second optical subcarrier frequency Interval compensation unit 5010, 6010, 7010 First polarization separation unit 5020, 6020, 7020 Second polarization separation unit 5210 Third optical carrier frequency deviation compensation unit 5220 Fourth optical carrier frequency deviation compensation unit 7430 Third Optical phase deviation compensation unit 7440 Fourth optical phase deviation Compensator 7450 Optical phase deviation adder 9000, 9500 Related optical phase deviation / optical carrier frequency deviation compensation device 9010 Optical subcarrier separation circuit 9100, 9200 Optical carrier frequency deviation compensation unit 9130, 9230 Optical phase deviation compensation unit 9510, 9520 Wave separation unit 100 Optical carrier frequency deviation compensation unit 110 Optical carrier frequency deviation compensation amount estimation unit 111 Optical carrier frequency error detection unit 112, 162 Filter unit 113 Phase compensation amount calculation unit 120, 170 Compensation execution unit 150 Related optical phase Deviation compensation unit 160 Optical phase deviation compensation amount estimation unit 161 Phase error detection unit

Claims

It is obtained by mixing and coherently detecting frequency division multiplexed signal light obtained by modulating and multiplexing a plurality of optical subcarriers having different frequencies including at least the first optical subcarrier and the second optical subcarrier. Separating means for receiving the frequency division multiplexed signal and outputting at least a first subcarrier signal and a second subcarrier signal;
First optical carrier frequency deviation compensating means for inputting the first subcarrier signal;
Second optical carrier frequency deviation compensating means for inputting the second subcarrier signal;
Optical subcarrier frequency interval compensation means connected to the first optical carrier frequency deviation compensation means and the second optical carrier frequency deviation compensation means,
The first optical carrier frequency deviation compensating means comprises: an optical phase deviation detecting means for detecting an optical phase change amount that is a change amount of an optical phase deviation between adjacent modulation signals in the first subcarrier signal; First compensation means for compensating for an optical carrier frequency deviation in the first subcarrier signal using first optical phase deviation information based on a phase change amount;
The optical subcarrier frequency interval compensation means calculates a frequency interval compensation amount for compensating an optical subcarrier frequency interval, which is a frequency difference between the first optical subcarrier and the second optical subcarrier,
The second optical carrier frequency deviation compensation means uses the second optical phase deviation information calculated from the frequency interval compensation amount and the first optical phase deviation information in the second subcarrier signal. An optical phase deviation / optical carrier frequency deviation compensator comprising second compensation means for compensating the optical carrier frequency deviation.
In the optical phase deviation / optical carrier frequency deviation compensation device according to claim 1,
The first optical carrier frequency deviation compensating means further includes a first phase compensation amount calculating means,
The first phase compensation amount calculating means calculates a first phase compensation amount by time-integrating the optical phase change amount as the first optical phase deviation information,
The first compensation means compensates for an optical carrier frequency deviation in the first subcarrier signal using the first phase compensation amount,
The optical subcarrier frequency interval compensation means acquires the optical phase change amount as the first optical phase deviation information from the first optical carrier frequency deviation compensation means, and is adjacent to the optical subcarrier frequency interval. The second optical phase deviation information is calculated by adding a value proportional to the product of the time interval between the modulation signals to the optical phase change amount as the frequency interval compensation amount, and calculating the second optical phase deviation information. Is sent to the second optical carrier frequency deviation compensating means,
The second optical carrier frequency deviation compensating means further includes second phase compensation amount calculating means,
The second phase compensation amount calculating means calculates a second phase compensation amount by time-integrating the second optical phase deviation information;
The second compensation means compensates for an optical carrier frequency deviation in the second subcarrier signal using the second phase compensation amount. An optical phase deviation / optical carrier frequency deviation compensation device.
In the optical phase deviation / optical carrier frequency deviation compensation device according to claim 1,
The first optical carrier frequency deviation compensating means further includes a first phase compensation amount calculating means,
The first phase compensation amount calculating means calculates the first phase compensation amount as the first optical phase deviation information by time-integrating the optical phase change amount,
The first compensation means compensates for an optical carrier frequency deviation in the first subcarrier signal using the first phase compensation amount,
The optical subcarrier frequency interval compensation unit obtains the first phase compensation amount from the first optical carrier frequency deviation compensation unit, and modulates the time interval between the optical subcarrier frequency interval and the adjacent modulation signal and the modulation. A value proportional to the product of the number of signals is added to the first phase compensation amount as the frequency interval compensation amount to calculate a second phase compensation amount as the second optical phase deviation information, and 2 phase compensation amount is sent to the second optical carrier frequency deviation compensating means,
The second compensation means compensates for an optical carrier frequency deviation in the second subcarrier signal using the second phase compensation amount. An optical phase deviation / optical carrier frequency deviation compensation device.
In the optical phase deviation / optical carrier frequency deviation compensation device according to claim 1,
The optical subcarrier frequency interval compensating means is connected to the first optical carrier frequency deviation compensating means and to the second optical carrier frequency deviation compensating means connected to the first optical carrier frequency deviation compensating means. Optical subcarrier frequency interval compensation means,
The first optical subcarrier frequency interval compensation means provides a first frequency interval compensation amount that compensates for a difference between an average frequency of the plurality of optical subcarriers and a frequency of the first optical subcarrier,
The second optical subcarrier frequency interval compensation means provides a second frequency interval compensation amount for compensating for a difference between an average frequency of the plurality of optical subcarriers and a frequency of the second optical subcarrier,
The first optical carrier frequency deviation compensating means further includes a first phase compensation amount calculating means,
The first phase compensation amount calculating means calculates the first phase compensation amount as the first optical phase deviation information by time-integrating the optical phase change amount,
The first compensation means compensates for an optical carrier frequency deviation in the first subcarrier signal using the first phase compensation amount,
The second compensation means compensates for an optical carrier frequency deviation in the second subcarrier signal using the first phase compensation amount as the second optical phase deviation information. Optical phase deviation / optical carrier frequency deviation Compensation device.
In the optical phase deviation / optical carrier frequency deviation compensation device according to any one of claims 1 to 4,
A first optical phase deviation compensation means on the path of the first subcarrier signal;
A second optical phase deviation compensation means on the path of the second subcarrier signal;
The first optical phase deviation compensation means compensates for an optical phase deviation in the first subcarrier signal based on the optical phase deviation compensation quantity, and an optical phase deviation compensation quantity estimation means for calculating an optical phase deviation compensation quantity. First phase compensation means for
The second optical phase deviation compensation means includes second phase compensation means,
The second phase compensation means is configured to add the second sub-carrier based on a value obtained by adding the optical phase deviation compensation amount to a phase deviation between the first optical sub-carrier and the second optical sub-carrier. Optical phase deviation / optical carrier frequency deviation compensation device for compensating optical phase deviation in a carrier signal.
In the optical phase deviation / optical carrier frequency deviation compensating device according to any one of claims 1 to 5,
Each of the plurality of optical subcarriers includes a first polarization optical subcarrier having a first polarization and a second polarization optical subcarrier having a second polarization orthogonal to the first polarization,
The first subcarrier signal includes a first polarized first subcarrier signal transmitted by the first polarized optical subcarrier and a first polarized first signal transmitted by the second polarized optical subcarrier. Including a subcarrier signal,
The second subcarrier signal includes a second polarized subcarrier signal transmitted by the first polarized optical subcarrier and a second polarized second signal transmitted by the second polarized optical subcarrier. Optical phase deviation / optical carrier frequency deviation compensation device including subcarrier signal.
In the optical phase deviation / optical carrier frequency deviation compensating apparatus according to claim 6,
The first optical carrier frequency deviation compensation means includes a first polarization separation means before the first optical carrier frequency deviation compensation means, and the second optical carrier frequency deviation compensation means precedes a second polarization separation means.
The first polarization separation means inputs the first subcarrier signal and outputs the first polarization first subcarrier signal and the second polarization first subcarrier signal;
The second polarization separation means inputs the second subcarrier signal, and outputs the second polarization subcarrier signal of the first polarization and the second subcarrier signal of the second polarization. Deviation and optical carrier frequency deviation compensation device.
In the optical phase deviation / optical carrier frequency deviation compensation device according to any one of claims 1 to 7,
A first number of the first optical carrier frequency deviation compensating means are provided,
The second optical carrier frequency deviation compensating means includes a plurality of second numbers which are plural,
A second number of optical subcarrier frequency interval compensation means are provided,
An optical phase deviation / optical carrier frequency deviation compensation device in which a sum of the first number and the second number is equal to the number of the plurality of optical subcarriers.
It is obtained by mixing and coherently detecting frequency division multiplexed signal light obtained by modulating and multiplexing a plurality of optical subcarriers having different frequencies including at least the first optical subcarrier and the second optical subcarrier. Receiving the frequency division multiplexed signal and outputting at least a first subcarrier signal and a second subcarrier signal;
An optical phase change amount that is a change amount of an optical phase deviation between adjacent modulation signals in the first subcarrier signal is detected, and the first optical phase deviation information based on the optical phase change amount is used to detect the first optical phase deviation amount. Compensates for the optical carrier frequency deviation in the subcarrier signal of
Calculating a frequency interval compensation amount for compensating an optical subcarrier frequency interval, which is a frequency difference between the first optical subcarrier and the second optical subcarrier,
Optical phase deviation / light which compensates optical carrier frequency deviation in the second subcarrier signal using the second optical phase deviation information calculated from the frequency interval compensation amount and the first optical phase deviation information Carrier frequency deviation compensation method.
In the optical phase deviation / optical carrier frequency deviation compensation method according to claim 9,
Calculating an optical phase deviation compensation amount in the first subcarrier signal, and compensating an optical phase deviation in the first subcarrier signal based on the optical phase deviation compensation amount;
The optical phase deviation in the second subcarrier signal is compensated based on a value obtained by adding the optical phase deviation compensation amount to the phase deviation between the first optical subcarrier and the second optical subcarrier. Optical phase deviation / optical carrier frequency deviation compensation method.