JP4990855B2 - Optical signal position detection method and optical signal position detection apparatus - Google Patents

Description

  The present invention mainly relates to an optical signal position detection method and an optical signal position detection apparatus that detect a signal position in optical transmission.

ここで、上付き添え字「＊」は複素共役を表す。
相関位置検出部２０３は、相関値ρ（ｔ）がピークとなる、時間ｔ０を算出し、信号位置決定部２０４に出力する。信号位置決定部２０４は、この時間ｔ０からマージン時間Δｔを引いた時間ｔ０−Δｔを信号の信号位置（先頭位置）として決定する。ここでΔｔは０以上の値とする。無線通信では、一般に、時間的に初めに受信される電波が最も強く受信されるため、上記方法で受信された信号の先頭位置を正確に得ることができる。この信号位置は、フーリエ変換などの信号処理が施される際の位置として決定される位置であって、信号位置の精度が信号処理の結果を左右する。このため、信号位置の精度が下がると、信号処理が適切な位置から実行されないため、干渉電力が増大する問題が生じる。
近年、上述した無線通での信号処理技術が、光通信において適用されつつあり、直交波周波数分割多重方式や、周波数領域等化を用いるシングルキャリア伝送などが検討され、光通信においても信号位置検出の需要が高まってきている。
Ｇｏｖｉｎｄ Ｐ．Ａｇｒａｗａｌ，“Ｎｏｎｌｉｎｅａｒ ｆｉｂｅｒ ｏｐｔｉｃｓ，”Ａｃａｄｅｍｉｃ ｐｒｅｓｓ，２００６，ｐｐ６３−６５，ｐｐ７６−７７． As an example of the prior art, a signal position detection method in wireless technology will be described with reference to FIG. FIG. 5 is a configuration example of a signal position detection apparatus in the conventional wireless communication technology.
As shown in FIG. 5, the conventional detection apparatus 200 includes an analog / digital conversion unit 201, a correlation value calculation unit 202, a correlation position detection unit 203, and a signal position determination unit 204.
The detection apparatus 200 converts an electrical signal received via the propagation path into a digital signal in the analog / digital conversion unit 201. The correlation value calculation circuit 202 calculates the correlation based on this digital signal. For example, a signal detection method in 802.11a of a wireless LAN is performed using a known signal sequence called a short preamble. Here, the known signal is defined as S (t). The known signal is a function of time t, and the time t is 0 ≦ t ≦ Ns−1. For the received signal X (t), the correlation value ρ (t) is calculated according to the following equation.

Here, the superscript “*” represents a complex conjugate.
The correlation position detection unit 203 calculates a time t0 when the correlation value ρ (t) reaches a peak, and outputs the time t0 to the signal position determination unit 204. The signal position determination unit 204 determines a time t0−Δt obtained by subtracting the margin time Δt from the time t0 as a signal position (leading position) of the signal. Here, Δt is a value of 0 or more. In wireless communication, generally, the first radio wave received first in time is received most strongly, so that the head position of the signal received by the above method can be obtained accurately. This signal position is a position determined as a position when signal processing such as Fourier transform is performed, and the accuracy of the signal position determines the result of the signal processing. For this reason, if the accuracy of the signal position is lowered, the signal processing is not executed from an appropriate position, which causes a problem that the interference power increases.
In recent years, the above-described wireless signal processing technology is being applied to optical communication, and orthogonal wave frequency division multiplexing, single carrier transmission using frequency domain equalization, and the like have been studied, and signal position detection is also used in optical communication. The demand for is increasing.
Govind P.M. Agrawal, “Nonlinear fiber optics,” Academic press, 2006, pp 63-65, pp 76-77.

However, in signal position detection in optical communication, when propagating through an optical fiber, the transmission speed varies depending on the wavelength of light due to the influence of chromatic dispersion, and a delay time occurs in the reception time from a high frequency to a low frequency in the receiver. Therefore, the above method has a problem that the signal position cannot be obtained accurately.
When such a phenomenon occurs, the correlation value rises slowly, peaks at the time when all the wavelength bands reach, and then decreases, so the peak position of the correlation value corresponds to the head position of the signal. However, there is a problem that the signal position cannot be accurately detected.
As described above, when the above method is applied to optical transmission, there is a problem that the signal position cannot be detected from the peak value of the correlation value because the correlation value is spread by chromatic dispersion.

  The present invention has been made in consideration of such circumstances, and has been made to solve the above-described problem. The purpose of the present invention is to distribute the correlation value even in communication via a propagation path in which the influence of chromatic dispersion exists. Thus, an optical signal position detection method and an optical signal position detection apparatus for detecting a signal position in consideration of the influence of chromatic dispersion are provided.

  The present invention also relates to an optical signal position detecting method in an optical signal position detecting device for detecting a signal position of a received signal received as an optical signal in an optical communication system, wherein the optical / electrical conversion of the optical signal position detecting device is performed. Unit converts the optical signal of the received signal into an electrical signal, and the signal sequence generation unit of the optical signal position detection device outputs a known signal that considers chromatic dispersion that is affected by chromatic dispersion caused by at least one path length. And a correlation value calculation unit of the optical signal position detection device calculates a correlation value between the chromatic dispersion-considered known signal stored in the signal sequence generation unit and the received signal, and detects the optical signal position. The correlation position detection unit of the apparatus outputs information on the peak position where the correlation value calculated by the correlation value calculation unit is maximum and the distribution of the correlation value, and the signal position determination unit of the optical signal position detection apparatus Based on the correlation value information output from the correlation position detection unit, the signal position of the received signal is detected and a function unit that guarantees the influence of chromatic dispersion is used, and a plurality of known signals considering chromatic dispersion are used. In this case, the optical signal position detection method is characterized in that a path length corresponding to a chromatic dispersion-considered known signal having a maximum correlation value is output.

  The present invention also relates to an optical signal position detecting method in an optical signal position detecting device for detecting a signal position of a received signal received as an optical signal in an optical communication system, wherein the optical / electrical conversion of the optical signal position detecting device is performed. The optical signal of the received signal is converted into an electrical signal, and the signal sequence generating unit of the optical signal position detecting device transmits and receives between the predetermined transmitting device that transmits the received signal and the optical signal position detecting device. A frequency shift detection known signal to which a plurality of frequency shifts that may occur in the optical signal position detection device are stored, and the correlation value calculation unit of the optical signal position detection device and the frequency shift detection known signal stored in the signal sequence generation unit The correlation value with the received signal is calculated, and the correlation position detection unit of the optical signal position detection device has information on the peak position where the correlation value calculated by the correlation value calculation unit is maximum and the distribution of the correlation value. And the signal position determination unit of the optical signal position detection device detects the signal position of the received signal and compensates for the frequency shift based on the correlation value information output from the correlation position detection unit. In the case of having a functional unit, the optical signal position detection method is characterized by outputting a frequency shift that occurs between the transmission and reception.

  The present invention also relates to an optical signal position detecting method in an optical signal position detecting device for detecting a signal position of a received signal received as an optical signal in an optical communication system, wherein the optical / electrical conversion of the optical signal position detecting device is performed. Unit converts an optical signal of the received signal into an electrical signal, and a signal sequence generation unit of the optical signal position detection device outputs a plurality of frequency domain divided known signals divided according to a frequency band in a predetermined known signal. A correlation value calculation unit of the optical signal position detection device calculates a correlation value between the plurality of frequency domain division known signals stored in the signal sequence generation unit and the reception signal, and the optical signal A correlation position detection unit of the position detection device outputs information on a peak position where the correlation value is maximum in each frequency domain division known signal calculated by the correlation value calculation unit, and the optical signal position detection When the signal position determination unit of the apparatus has a function unit that detects the signal position of the received signal and compensates for the influence of chromatic dispersion based on the information of the plurality of correlation values output from the correlation position detection unit Is a method for detecting the position of an optical signal, characterized by outputting information on a shift in peak position.

Further, the present invention provides an optical signal position detection device that detects a signal position of a received signal received as an optical signal in an optical communication system, and an optical / electrical converter that converts the optical signal of the received signal into an electrical signal ; wavelength dispersion wavelength dispersion considered known signal effect is given of a frequency shift that can occur between the transmission and reception of a plurality of predetermined transmission apparatus that transmits the received signal to a Jo Tokoro of the known signal and the optical signal position detecting device The given frequency deviation detection known signal, the plurality of chromatic dispersion frequency domain known signals obtained by giving a plurality of frequency deviations to the predetermined known signal, and the predetermined known signal being divided according to a frequency band A plurality of frequency domain division known signals, or a signal sequence generation unit that stores at least one of the plurality of frequency domain division known signals given the plurality of frequency shifts; and Signal sequence generating unit before Symbol wavelength dispersion considering the known signal that has been stored in the frequency deviation detection known signals, said plurality of wavelength dispersion frequency domain known signal or at least one of the plurality of frequency domain division known signal, the A correlation position detection unit that calculates a correlation value with a received signal and outputs information on a peak position where the correlation value calculated by the correlation value calculation unit is maximum or a distribution of a peak position and a correlation value; and the correlation And a signal position determination unit that detects a signal position of the received signal based on the correlation value information output from the position detection unit.

According to the present invention, it is possible to evaluate the influence of chromatic dispersion and detect the signal position by obtaining the peak position of the correlation value and the spread of the distribution of the correlation value.
In addition, according to the present invention, taking into account the frequency shift that occurs between transmission and reception, by calculating the correlation between a plurality of frequency shift detection known signals multiplied by the influence of the frequency shift and the received signal, the magnitude of the correlation value can be calculated. The frequency shift between transmission and reception can be determined. Also, by calculating the correlation between the received signal and multiple frequency domain division known signals obtained by dividing the known signal into bands, the influence of chromatic dispersion can be determined from the deviation of the peak position of the correlation value in each frequency band. Thus, the influence of chromatic dispersion can be evaluated based on the correlation with the known signal obtained by band division.
In addition, by calculating the correlation between the received signal and the chromatic dispersion-considered known signal that is affected by the chromatic dispersion corresponding to a plurality of path lengths, the influence of the chromatic dispersion can be evaluated from the magnitude of the correlation value. it can.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of an optical signal position detection apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a correlation value distribution using a known signal.

As shown in FIG. 1, an optical signal position detection apparatus 100 includes an optical / electrical conversion unit 101, an A / D conversion unit 102, a signal sequence generation unit 103, a correlation value calculation unit 104, a correlation position detection unit 105, and a signal position determination unit. 106.
The optical / electrical converter 101 receives an optical signal transmitted through an optical fiber, converts the received signal from an optical signal to an electrical signal, and outputs the electrical signal.
The A / D conversion unit (analog / digital signal conversion unit) 102 converts the electrical signal output from the optical / electrical conversion unit 101 from an analog signal to a digital signal and outputs the signal. Hereinafter, a signal output from the A / D conversion unit 102 is defined as X (t).
The signal sequence generation unit 103 stores a plurality of known signals according to the correlation value ρ calculated by the correlation value calculation unit 104. Here, the known signal is defined by S (t) and is a function of time t. The time t is in the range of 0 ≦ t ≦ Ns−1. Ns represents the length of the known signal.

これは、受信信号Ｘ（ｔ）と既知信号Ｓ（ｔ）に基づき、相関値ρ（ｔ）を算出する演算式を示している。
なお、上付き添え字「＊」は複素共役を表す。式１において、分母に示す｜Ｓ（ｔ）｜の総和は、時間によらず一定となるため、省略することができ、分母に示す｜Ｘ（ｔ−ｉ）｜の総和についても、受信レベルが大きく変動しない場合は無視することができる。 Correlation value calculation section 104 calculates the correlation between the received signal and a known signal stored in advance. That is, correlation value calculation section 104 calculates the correlation between the received signal output from A / D conversion section 102 and the known signal read from signal sequence generation section 103, and outputs correlation value ρ. For example, the correlation value calculation unit 104 calculates the correlation value ρ as a calculation formula for the correlation value ρ set in advance according to Formula 1 shown below.

This shows an arithmetic expression for calculating the correlation value ρ (t) based on the received signal X (t) and the known signal S (t).
The superscript “*” represents a complex conjugate. In equation 1, the sum of | S (t) | shown in the denominator is constant regardless of time, and can be omitted. The sum of | X (t−i) | If it does not fluctuate significantly, it can be ignored.

このように、信号位置決定部１０６は、ピーク位置ｔｐからマージン時間Δｔを引いた時間ｔｐ−Δｔの床関数を先頭位置ｔｓとして決定する。Δｔは０以上の値とする。 The correlation position detection unit 105 detects a peak time at which the correlation value ρ output from the correlation value calculation unit 104 peaks, that is, a peak position tp. Further, the correlation position detection unit 105 outputs the detected peak position tp or correlation value information around the peak position tp to the variance value calculation unit 106.
The signal position determination unit 106 detects the head position of the received signal based on the correlation value information around the peak position tp detected by the correlation position detection unit 105. For example, as shown in FIG. 2, the correlation position detection unit 105 calculates a time interval T at which the correlation value is greater than or equal to ρp / M before and after the peak position tp based on the correlation value ρp at the peak position tp. M is an arbitrary constant. Based on this time interval T, the signal position determination unit 106 calculates the margin time Δt according to Equation 3, and calculates the head position ts of the signal according to Equation 2.

As described above, the signal position determination unit 106 determines the floor function of the time tp−Δt obtained by subtracting the margin time Δt from the peak position tp as the head position ts. Δt is 0 or more.

  The margin time Δt is a value representing how far in front of or behind the peak position tp is regarded as the head of the signal. Moreover, the right side shown in Formula 2 is a floor function, and represents the meaning of the maximum integer that does not exceed (tp−Δt). Further, B shown in Expression 3 is a positive constant of 1 or more, and is determined by, for example, how much the influence due to chromatic dispersion is allowed. A large value is set in order to reduce interference due to chromatic dispersion. Is done.

In addition, when the guard interval is used for the signal series, the signal position determination unit 106 determines the head position ts in consideration of the guard interval. For example, when the guard interval is used only for the time interval G, the signal position determination unit 106 needs to determine the window position so that the variance is most contained in the guard interval. Determined according to Equation 4 shown.

Here, it demonstrates concretely using FIG. In FIG. 2, the optical signal position detection apparatus 100 receives an optical signal transmitted at 12.5 G [sample / sec] and propagated through an optical fiber of 1600 km at 25 G [sample / sec]. Shows data obtained by calculating a correlation value ρ with respect to time t [sample] based on this transmission signal and according to the arithmetic expression of Expression 1. Here, time t = 1 [sample] corresponds to 40 psec.
As shown in FIG. 2, the peak of the correlation value ρ is ρp = 5.6, and the peak position tp at that time is tp = 540 [sample]. A signal spreads before and after the peak position tp in the time axis direction. This is due to the influence of chromatic dispersion caused by the propagation of the optical fiber. Here, the reason why the correlation value is larger than 1 is that the calculation of the denominator is omitted in Equation 1.

The signal position determination unit 106 detects the peak position tp = 540 [sample] and the correlation value (peak value) ρp = 5.6 at that time, and before and after tp = 540 [sample], the correlation value ρ = ρp / A time interval T for M is calculated. When M = 2, when 520 ≦ t ≦ 566, ρp = 5.6 / 2 or more.
Therefore, in this case, correlation value calculation section 105 outputs the signal spread for time interval T = 47 [sample] as correlation value information around peak position tp.
Based on this correlation value information, the signal position determination unit 106 estimates the head position ts from Equations 2 and 3 and sets the head position ts = 505 [sample] when B = 1.5. When the guard interval is used for 64 counts, the signal position determination unit 106 calculates the head position ts = 508 [sample] according to Equation 4.

Next, the optical signal position detection method in the optical signal position detection apparatus 100 according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing an example of an optical signal position detection method according to the present invention.
As shown in FIG. 3, when the optical signal position detection device 100 receives a reception signal, the optical / electrical conversion unit 101 converts the optical signal into an electric signal and outputs it to the A / D conversion unit 102 (S1). When the A / D converter 102 receives the electrical signal, the A / D converter 102 converts the analog signal into a digital signal and outputs it to the correlation value calculator 104 (S2). Correlation value calculation section 104 calculates correlation value ρ based on the received signal received from A / D conversion section 102 and the known signal read from signal sequence generation section 103, and outputs the correlation value ρ to correlation position detection section 105 (S3). ). The correlation position detection unit 105 detects the peak position tp based on the correlation value ρ, and outputs the peak position tp or correlation value information around the peak position tp to the signal position determination unit 106 (S4).
Based on the received correlation value information, the signal position determination unit 106 determines the head position ts of the received signal from Expression 2 or 4, and outputs it (S5).

[Second Embodiment]
Next, another embodiment according to the present invention will be described. Note that the optical signal position detection device in the present embodiment has the same configuration as the optical signal position detection device 100 described in the first embodiment, and detailed description of the configuration is omitted by attaching the same reference numerals.
The optical signal position detection apparatus according to the present embodiment has the following configuration and function in order to obtain a higher correlation value by giving the known signal the influence of chromatic dispersion caused by the path length. Yes. In the case where the optical signal position detection device uses a plurality of chromatic dispersion-considered known signals, by obtaining a path length corresponding to the chromatic dispersion-considered known signal that maximizes the correlation value, any externally connected arbitrary signal is obtained. A function unit (not shown) that guarantees the influence of chromatic dispersion can compensate for the influence of chromatic dispersion by using this path length.

ここで、位相θ（ｆ）は、波長分散による位相オフセット値であり、非特許文献１記載のように伝送経路である光ファイバの長さ及び光ファイバの波長分散値、波長分散スロープ値に合わせて算出することができる。Ｓｆ´（０）、Ｓｆ´（１），・・・Ｓ´（Ｎｓ−１）を逆フーリエ変換により時間領域に変換することで、波長分散周波数領域既知信号Ｓ´（０）、Ｓ´（１），・・・Ｓ´（Ｎｓ−１）を得ることできる。相関値演算部１０４は、波長分散周波数領域既知信号Ｓ´（０）、Ｓ´（１），・・・Ｓ´（Ｎｓ−１）を用いて、下に示す式６に従い、相関値ρを算出する。

ここで、分母の値の時間による変動が小さい場合には、無視することができる。 The signal sequence generation unit 103 stores chromatic dispersion-considered known signals S ′ (0), S ′ (1),..., S ′ (Ns−1) to which a delay due to frequency is given in consideration of chromatic dispersion. To do.
The known signals S ′ (0), S ′ (1),..., S ′ (Ns−1) in consideration of chromatic dispersion are known signals S (0), S (1),. -1). By using Fourier transform for the known signals S (0), S (1),..., S (Ns−1), which are time domain signals, the frequency domain known signals Sf (0), Sf (1). ,..., Sf (Ns−1) are obtained, and the phase shift corresponding to the delay due to chromatic dispersion is further converted into the known signals Sf (0), Sf (1),. ) To obtain chromatic dispersion frequency domain known signals S ′ (0), S ′ (1),... S ′ (Ns−1). At this time, an arithmetic expression of the following expression (Expression 5) can be used.
It shows with.

Here, the phase θ (f) is a phase offset value due to chromatic dispersion, and matches the length of the optical fiber, the chromatic dispersion value of the optical fiber, and the chromatic dispersion slope value as described in Non-Patent Document 1. Can be calculated. By converting Sf ′ (0), Sf ′ (1),... S ′ (Ns−1) into the time domain by inverse Fourier transform, chromatic dispersion frequency domain known signals S ′ (0), S ′ ( 1),... S ′ (Ns−1) can be obtained. The correlation value calculation unit 104 uses the chromatic dispersion frequency domain known signals S ′ (0), S ′ (1),... S ′ (Ns−1), and calculates the correlation value ρ according to Equation 6 below. calculate.

Here, when the variation of the denominator value with time is small, it can be ignored.

  The signal position determination unit 106 detects the front end position ts of the received signal based on the correlation value ρ output from the correlation position detection unit 105. In addition, the signal position determination unit 106 includes a function unit (not shown) that guarantees the influence of arbitrary chromatic dispersion connected to the outside of the optical signal position detection device, and uses a plurality of chromatic dispersion-considered known signals. Output the path length corresponding to the chromatic dispersion-considered known signal having the maximum correlation value ρ.

  As described above, the optical signal position detection apparatus according to the present embodiment obtains a higher correlation value by using a known signal with a delay due to a frequency considering chromatic dispersion as a known signal for obtaining the correlation value ρ. be able to.

[Third Embodiment]
Next, another embodiment according to the present invention will be described. Note that the optical signal position detection device in the present embodiment has the same configuration as the optical signal position detection device 100 described in the first embodiment, and detailed description of the configuration is omitted by attaching the same reference numerals.
The optical signal position detection apparatus according to the present embodiment detects a frequency shift corresponding to the phase offset φa having the largest correlation value when detecting a frequency shift of light occurring in the reception apparatus and the transmission apparatus, and In order to detect the leading position ts, the following configuration / function is provided.

ここで、Ｎｓは、周波数チャネル数であり、φａは、周波数ずれに対応する位相オフセット値であり、−π＜φａ＜πである。
相関値演算部１０４は、周波数ずれ検知既知信号Ｓ´´ａ（ｔ）に基づき、下に示す式８に従い、相関値ρを算出する。

ここで、分母の値の時間変動が小さい場合には、分母を無視することができる。
すなわち、相関値演算部１０４は、時系列の既知信号系列Ｓ（ｔ）に位相オフセット値φａが付加された周波数ずれ検知既知信号Ｓ´´ａ（ｔ）を用いて、相関値ρを算出し、相関値のピーク位置の精度を高めることができる。
また、相関値演算部１０４は、時系列の既知信号系列に位相オフセットを付加することにより、相関値が最も大きくなる位相オフセットφａに対応する周波数ずれを検出することができる。
さらに、信号位置決定部１０６は、光信号位置検出装置の外部に接続されている任意の周波数ずれを補償する機能部（図示せず）を備えている場合、送受信間で生じる周波数ずれを出力する。 The signal series generation unit 103 stores the frequency deviation detection known signals S ″ a (0), S ″ a (1),..., S ″ a (Ns−1). Here, 1 ≦ a ≦ Na, and the signal sequence generation unit 103 stores a frequency shift detection signal S ″ a (t) corresponding to Na frequency shifts.
This frequency shift detection known signal S ″ a (t) is expressed by the following equation (Equation 7).

Here, Ns is the number of frequency channels, φa is a phase offset value corresponding to the frequency shift, and −π <φa <π.
The correlation value calculation unit 104 calculates the correlation value ρ according to Equation 8 below based on the frequency shift detection known signal S ″ a (t).

Here, when the time variation of the denominator value is small, the denominator can be ignored.
That is, the correlation value calculation unit 104 calculates the correlation value ρ using the frequency shift detection known signal S ″ a (t) obtained by adding the phase offset value φa to the time-series known signal sequence S (t). The accuracy of the peak position of the correlation value can be improved.
Further, the correlation value calculation unit 104 can detect a frequency shift corresponding to the phase offset φa at which the correlation value becomes the largest by adding a phase offset to the time-series known signal sequence.
Furthermore, when the signal position determination unit 106 includes a function unit (not shown) that compensates for an arbitrary frequency shift connected to the outside of the optical signal position detection apparatus, the signal position determination unit 106 outputs a frequency shift that occurs between transmission and reception. .

[Fourth Embodiment]
Next, another embodiment according to the present invention will be described. Note that the optical signal position detection device in the present embodiment has the same configuration as the optical signal position detection device 100 described in the first embodiment, and detailed description of the configuration is omitted by attaching the same reference numerals.
The optical signal position detection apparatus according to the present embodiment uses the known signal divided according to the frequency domain, determines the influence of chromatic dispersion from the magnitude of the correlation value, and detects the leading position ts of the signal. Therefore, it has the following configuration / function.

ここで、分母の値の時間変動が小さい場合には、分母を無視することができる。
このとき、異なる周波数領域に対応する周波数領域分割既知信号Ｓ´´´ｃ（ｔ）では、相関値ρのピーク位置が異なる。 The signal sequence generation unit 103 includes a plurality of frequency domain division known signals S ″ ″ c (0), S ″ ″ c (1),. Ns-1) is stored. This frequency domain division known signal S ″ ″ c (t) is obtained by subjecting the known signal series S (0) to S (Ns−1) to digital processing such as a low pass filter, a high pass filter, and a band pass filter. Alternatively, conversion from the known signals S ′ (0), S ′ (1),..., S ′ (Ns−1) in consideration of chromatic dispersion into the time domain is performed again using a signal in only an arbitrary frequency domain. Is calculated in advance and stored in the signal sequence generation unit 103. Note that 1 ≦ c ≦ Nfb, and the signal sequence generation unit 103 stores frequency domain division known signals S ′ ″ c (t) corresponding to Nfb frequency domains.
Correlation value calculation section 104 calculates correlation value ρ according to Equation 10 shown below based on a plurality of frequency domain division known signals S ″ ″ (t) read from signal sequence generation section 103.

Here, when the time variation of the denominator value is small, the denominator can be ignored.
At this time, the peak positions of the correlation values ρ are different in the frequency domain division known signal S ′ ″ c (t) corresponding to different frequency domains.

Here, it demonstrates concretely using FIG. In FIG. 4, the optical signal position detection apparatus 100 receives an optical signal transmitted at 12.5 [sample / sec] and propagated through an optical fiber of 1600 km at 25 G [sample / sec]. However, based on this transmission signal, using the frequency domain division known signals S ″ ″ 1 (t) and S ″ ″ 2 (t) corresponding to two frequency bands, the time t The data which calculated correlation value (rho) with respect to [sample] are shown. Here, the time t [sample] corresponds to 40 psec.
As shown in FIG. 4, the correlation value ρ of the frequency band A corresponding to the frequency domain division known signal S ″ ″ 1 (t) and the frequency band B corresponding to the frequency domain division known signal S ″ ″ 2 (t) The peak is shifted The correlation position detection unit 105 detects the peak positions tp1 and tp2 of the correlation value ρ in the corresponding frequency band (frequency bands A and B).
The signal position determination unit 106 uses the center between the peak positions tp1 and tp2 as the peak position tp and the interval between the peak positions tp1 and tp2 as the time interval T, and the signal start position ts according to Equations 2 and 3. Is detected.
Further, when the signal position determination unit 106 includes a function unit (not shown) that compensates for the influence of arbitrary chromatic dispersion connected to the outside of the optical signal position detection device, it outputs peak position deviation information. To do.
In this way, the optical signal position detection device according to the present embodiment uses the peak of the correlation value ρ calculated using the frequency domain division known signal S ″ ″ c (t) divided according to the frequency domain. From the position shift, it is possible to evaluate the influence of chromatic dispersion and detect the leading position ts of the signal.

検出されたピーク位置に基づき得られたガードインターバルの時間間隔Ｇから式４により信号位置を決定できる。 [Fifth Embodiment]
Next, another embodiment according to the present invention will be described. Note that the optical signal position detection device in the present embodiment has the same configuration as the optical signal position detection device 100 described in the first embodiment, and detailed description of the configuration is omitted by attaching the same reference numerals. Further, unlike the first embodiment, the optical signal position detection apparatus in the present embodiment does not require the signal sequence generation unit 103 and the known signal shown in FIG.
The optical signal position detection apparatus according to the present embodiment detects the signal start position ts based on the cross-correlation value ρc calculated by the cross-correlation of the received signal based on the received optical signal. It is characterized by having.
Correlation value calculation section 104 calculates a cross-correlation value ρc between a plurality of received signals based on optical signals received after a predetermined time. That is, correlation value calculation section 104 calculates cross-correlation value ρc according to the calculation expression of Expression 11 shown below.

The signal position can be determined by Equation 4 from the time interval G of the guard interval obtained based on the detected peak position.

In addition, the optical signal position detection apparatus according to the present invention can be used in combination of the above-described embodiments. For example, chromatic dispersion consideration known signals S ′ (0), S ′ (1),..., S ′ (Ns−1) and frequency domain division known signals S ″ ″ c (0), S ″ ″. Signals obtained by multiplying c (1),..., S ″ ″ (Ns−1) by the phase offset value corresponding to the frequency shift as shown in Expression 7 Can be remembered.
In the above-described embodiment, the signal position determination unit 103 has been described by taking an example of a configuration in which an arbitrary known signal is stored in advance. However, the present invention is not limited to this, and based on the stored known signal, wavelength dispersion A known signal S ′ (t) to be considered, a chromatic dispersion frequency domain known signal Sf ′ (t), a frequency shift detection known signal S ″ a (t), and a frequency domain division known signal S ″ ″ c (t) are generated. It may be a configuration.
For example, when using the known signal divided according to the frequency band as described with reference to the fourth embodiment, the signal sequence generation unit 103 is combined with the third embodiment in accordance with Equation 7 or Equation 9 is applied to the frequency deviation detection known signal S ″ a (t) obtained in accordance with 9, and a digital processing such as a low-pass filter, a high-pass filter, and a band-pass filter is performed to obtain the frequency domain division known signal S ″ ″ c (t). The structure to produce | generate may be sufficient.
In addition, the signal sequence generation unit 103 calculates the chromatic dispersion-considered known signal S ′ (0) according to Equation 5 in combination with the second and fourth embodiments, and then uses a signal of only an arbitrary frequency to generate a time domain. The frequency domain division known signal S ′ ″ c (t) may be generated by converting again to.
As described above, according to the present invention, the head position of a signal can be detected based on the received signal in optical communication.

It is a block diagram which shows an example of a structure of this Embodiment. It is the schematic which shows correlation value distribution using the known signal concerning this Embodiment. It is a flowchart which shows an example of the optical signal position detection method in the optical signal position detection apparatus concerning this Embodiment. It is the schematic which shows the correlation value distribution using the known signal divided | segmented according to the frequency band concerning this Embodiment. It is a block diagram which shows an example of the conventional signal position detection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical signal position detection apparatus 101 Opto-electric conversion part 102 A / D conversion part 103 Signal sequence generation part 104 Correlation value calculation part 105 Correlation position detection part 106 Signal position determination part

Claims (4)

In an optical communication method, an optical signal position detection method in an optical signal position detection device for detecting a signal position of a received signal received as an optical signal,
The optical / electrical converter of the optical signal position detecting device is
Converting the optical signal of the received signal into an electrical signal;
The signal sequence generation unit of the optical signal position detection device,
Storing a known signal in consideration of chromatic dispersion given the influence of chromatic dispersion caused by at least one path length;
The correlation value calculation unit of the optical signal position detection device,
Calculating a correlation value between the chromatic dispersion-considered known signal stored in the signal sequence generation unit and the received signal;
The correlation position detection unit of the optical signal position detection device,
Output the peak position where the correlation value calculated by the correlation value calculation unit is maximum and the distribution of the correlation value,
The signal position determination unit of the optical signal position detection device,
Based on the correlation value information output from the correlation position detection unit, the signal position of the received signal is detected and a function unit that guarantees the influence of chromatic dispersion is used, and a plurality of known signals considering chromatic dispersion are used. In this case, a path length corresponding to a chromatic dispersion-considered known signal having a maximum correlation value is output. In an optical communication method, an optical signal position detection method in an optical signal position detection device for detecting a signal position of a received signal received as an optical signal,
The optical / electrical converter of the optical signal position detecting device is
Converting the optical signal of the received signal into an electrical signal;
The signal sequence generation unit of the optical signal position detection device,
Storing a frequency deviation detection known signal to which a plurality of frequency deviations that may occur between transmission and reception between the predetermined transmission device that transmits the reception signal and the optical signal position detection device are given;
The correlation value calculation unit of the optical signal position detection device,
Calculating a correlation value between the received signal and the frequency deviation detection known signal stored in the signal sequence generation unit;
The correlation position detection unit of the optical signal position detection device,
Output the peak position where the correlation value calculated by the correlation value calculation unit is maximum and the distribution of the correlation value,
The signal position determination unit of the optical signal position detection device,
Based on the correlation value information output from the correlation position detector, detects the signal position of the received signal and outputs a frequency shift that occurs between the transmission and reception when the function unit compensates the frequency shift. An optical signal position detection method. In an optical communication method, an optical signal position detection method in an optical signal position detection device for detecting a signal position of a received signal received as an optical signal,
The optical / electrical converter of the optical signal position detecting device is
Converting the optical signal of the received signal into an electrical signal;
The signal sequence generation unit of the optical signal position detection device,
Storing a plurality of frequency domain divided known signals divided according to a frequency band in a predetermined known signal;
The correlation value calculation unit of the optical signal position detection device,
Calculating a correlation value between the plurality of frequency domain division known signals stored in the signal sequence generation unit and the received signal;
The correlation position detection unit of the optical signal position detection device,
Output the information of the peak position where the correlation value in each frequency domain division known signal calculated by the correlation value calculation unit is maximized,
The signal position determination unit of the optical signal position detection device,
Based on the information of the plurality of correlation values output from the correlation position detection unit, the signal position of the received signal is detected, and a function unit that compensates for the influence of chromatic dispersion is provided. An optical signal position detection method characterized by outputting information. In an optical communication system, in an optical signal position detection device that detects a signal position of a received signal received as an optical signal,
An optical / electrical converter that converts an optical signal of the received signal into an electrical signal;
Wavelength dispersion wavelength dispersion considered known signal effect is given of a frequency shift that can occur between the transmission and reception of a plurality of predetermined transmission apparatus that transmits the received signal to a Jo Tokoro of the known signal and the optical signal position detecting device The given frequency deviation detection known signal, the plurality of chromatic dispersion frequency domain known signals obtained by giving a plurality of frequency deviations to the predetermined known signal, and the predetermined known signal being divided according to a frequency band A plurality of frequency domain division known signals, or a signal sequence generation unit that stores at least one of the plurality of frequency domain division known signals given the plurality of frequency shifts;
The signal sequence generating unit before Symbol wavelength dispersion considering the known signal that has been stored in the frequency deviation detection known signals, said plurality of wavelength dispersion frequency domain known signal or at least one of the plurality of frequency domain division known signal, Calculating a correlation value with the received signal;
A correlation position detection unit that outputs information on a peak position where the correlation value calculated by the correlation value calculation unit is maximum, or a distribution of a peak position and a correlation value;
An optical signal position detecting device comprising: a signal position determining unit that detects a signal position of the received signal based on the correlation value information output from the correlation position detecting unit.

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