JP2016178586A - Fm batch conversion signal quality estimation device, method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate the quality of FM batch conversion signal at a low cost, in a realistic time, even when the transmission carrier plan of FM batch conversion system is changed in an optical transmission system being provided.SOLUTION: At first, an unmodulated signal estimation unit 1 estimates the frequency dependence D(f) of the Duty ratio of an unmodulated sinusoidal signal after transmission in the use band of a FM batch conversion signal, and after a FM signal calculation unit 2 calculated the instantaneous frequency f(T) and the sign of a slope a(T) at the zero cross time Tof the FM batch conversion signal before transmission, a zero cross time shift amount estimation unit 3 estimates the shift amount dT(T) at the zero cross time Tof the FM batch conversion signal before and after transmission, based on these estimates and calculation values. Next, a frequency spectral leakage amount estimation unit 5 estimates the CNR_related to self-phase modulation and wavelength dispersion. Next, a FM demodulation signal estimation unit 7 estimates the CNR_related to all elements of an optical transmission system containing the optical amplification noise.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a technique for estimating the quality of an FM batch conversion signal in an optical transmission system that transmits frequency-multiplexed multi-channel signals using the FM batch conversion method.

  The transmission method used in the optical video distribution system includes (1) an intensity modulation method in which an optical carrier wave is intensity-modulated by a frequency-multiplexed multi-channel video signal, and (2) a frequency-multiplexed multi-channel video signal. Is converted into a broadband FM signal having an FM carrier signal frequency of 3 GHz, and the FM carrier signal is intensity-modulated and transmitted by the broadband FM signal obtained by the conversion (see Non-Patent Document 1). There is. Hereinafter, the FM batch conversion method is used.

  By the way, with the spread of the FTTH network in recent years, the introduction of the optical video distribution system into the FTTH network is progressing as being capable of transmitting a high-capacity video signal with a large number of channels. In the optical video distribution system, the transmission distance is required to be extended from the viewpoint of area expansion. Furthermore, in an optical video distribution system using the FM batch conversion method, long-distance optical transmission is possible by connecting optical amplification devices in multiple stages.

JP 2011-151600 A

Satoshi Ikeda, Takato Kawatsuki, Kaori Izutsu, Toshiaki Shimoha, “Wide-area video distribution using FM batch conversion technology”, [online], May 2007, NTT Technical Journal, [March 6, 2015] ] <Internet: <URL: http: // www. ntt. co. jp / journal / 0705 / files / jn200705044. pdf # search = '% EF% BC% A6% EF% BC% AD% E4% B8% 80% E6% 8B% AC% E5% A4% 89% E6% 8F% 9B +% EF% BC% AE% EF% BC% B4% EF% BC% B4 '> Sugawarayama, “FM Radio Engineering”, Nikkan Kogyo Shimbun, pp. 16-18

  In Patent Document 1, in an optical video distribution system using an FM batch conversion method in which optical amplifiers are connected in multiple stages and an optical signal is transmitted over a long distance with relatively high intensity, the quality of FM demodulated signals (specifically, A technique for estimating (CNR) is disclosed.

  In Patent Document 1, first, a technique for estimating a CNR related to optical noise amplification is disclosed. However, waveform estimation due to the combined effect of self-phase modulation and chromatic dispersion cannot be considered only by estimating the CNR related to optical noise amplification, and the CNR of the FM demodulated signal is estimated in a better direction than the actually generated CNR. End up. Therefore, it is conceivable to obtain the time waveform of the FM batch conversion signal after transmission by solving the nonlinear Schrodinger equation by numerical calculation for the time waveform of the FM batch conversion signal before transmission. However, since the FM batch conversion signal before transmission has a very complicated frequency spectrum (see Non-Patent Document 2), the nonlinear Schrodinger equation is extremely complicated and requires a large amount of calculation time.

  Patent Document 1 discloses a technique for estimating CNR related to self-phase modulation and chromatic dispersion. Here, the waveform collapse due to the combined effect of self-phase modulation and chromatic dispersion is estimated as the zero-cross time shift amount of the unmodulated FM carrier signal before and after transmission, or as the duty ratio of the unmodulated FM carrier signal after transmission. . Before that, the dependency of CNR related to self-phase modulation and chromatic dispersion on the duty ratio of the unmodulated FM carrier signal after transmission is “measured in advance”. Therefore, the CNR related to self-phase modulation and chromatic dispersion can be estimated based on the estimated duty ratio and the “pre-measured” dependency. Based on the CNR related to optical noise amplification and the CNR related to self-phase modulation and chromatic dispersion, the CNR related to all elements of the optical video distribution system can be estimated quantitatively in a short time.

  As described above, in Patent Document 1, it is necessary to “measure in advance” the dependency of CNR related to self-phase modulation and chromatic dispersion on the duty ratio of an unmodulated FM carrier signal after transmission. By the way, the transmission carrier plan of the FM batch conversion method may be changed in the optical video distribution system being provided. Then, since the frequency spectrum of the FM batch conversion signal changes, the leakage amount of the frequency spectrum of the FM batch conversion signal with respect to the frequency spectrum of the FM demodulated signal also changes, and the “measured in advance” dependency also changes. Therefore, every time the FM carrier conversion scheme transmission carrier plan is changed, it is necessary to “measure again” the dependency, which causes a problem of high costs such as human operation and measurement time.

  Therefore, in order to solve the above-described problems, the present invention provides an FM batch process in a low cost and within a realistic time even when a transmission carrier plan of the FM batch conversion method is changed in a provided optical transmission system. An object of the present invention is to provide a technique for estimating the quality of a converted signal.

  In order to achieve the above object, the frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal is estimated, and the instantaneous instant at the zero crossing time of the FM batch conversion signal before transmission is estimated. After calculating the frequency and the sign of the slope, the deviation amount of the zero crossing time of the FM batch conversion signal before and after transmission is estimated based on these estimated values and calculated values.

  Specifically, the present invention is an FM batch conversion signal quality estimation apparatus that estimates the quality of the FM batch conversion signal after the FM batch conversion signal is transmitted in an optical transmission system, the FM batch conversion signal , A non-modulated signal estimator for estimating the frequency dependence of the duty ratio of an unmodulated sine wave signal after transmission, a zero-cross time of the FM batch converted signal before transmission, and the FM batch before transmission An FM signal calculation unit that calculates an instantaneous frequency at the zero crossing time of the converted signal and a sign of a slope at the zero crossing time of the FM batch conversion signal before transmission, and a post-transmission estimated by the unmodulated signal estimation unit The frequency dependence of the duty ratio of the unmodulated sine wave signal, the instantaneous frequency at the zero crossing time of the FM batch conversion signal before transmission calculated by the FM signal calculation unit, and the FM signal meter A zero-cross time shift estimation unit that estimates the shift amount of the zero-cross time of the FM batch conversion signal before and after transmission based on the sign of the slope at the zero-cross time of the FM batch conversion signal before transmission calculated by the unit; The FM batch conversion signal quality estimation apparatus comprising:

  Specifically, the present invention is an FM batch conversion signal quality estimation method for estimating the quality of the FM batch conversion signal after the FM batch conversion signal is transmitted in an optical transmission system, and the FM batch conversion signal , A non-modulated signal estimation step for estimating the frequency dependence of the duty ratio of an unmodulated sine wave signal after transmission, the zero-cross time of the FM batch conversion signal before transmission, and the FM batch before transmission FM signal calculation step for calculating the instantaneous frequency at the zero-crossing time of the converted signal and the sign of the slope at the zero-crossing time of the FM batch conversion signal before transmission, and the post-transmission estimated by the unmodulated signal estimation step The frequency dependence of the duty ratio of the unmodulated sine wave signal and the instant at the zero crossing time of the FM batch conversion signal before transmission calculated by the FM signal calculation step Based on the wave number and the sign of the slope at the zero crossing time of the FM batch conversion signal before transmission calculated by the FM signal calculation step, the amount of shift of the zero batch time of the FM batch conversion signal before and after transmission is estimated. An FM batch conversion signal quality estimation method comprising: a zero-cross time lag estimation step.

  According to this configuration, it is not necessary to “measure in advance” the dependency of CNR related to self-phase modulation and chromatic dispersion on the duty ratio of an unmodulated FM carrier signal after transmission. For the time waveform of the unmodulated sine wave signal before transmission, it is sufficient to obtain the time waveform of the unmodulated sine wave signal after transmission by solving the nonlinear Schrodinger equation by numerical calculation.

  Further, the present invention provides a difference between a zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation unit and a zero cross time of the FM batch conversion signal before and after transmission estimated by the zero cross time shift estimation unit. A delay detection time waveform estimation unit that estimates a delay detection time waveform of the FM batch conversion signal after transmission based on the amount, and the FM batch conversion signal after transmission estimated by the delay detection time waveform estimation unit A frequency spectrum for estimating a leak amount of the frequency spectrum of the FM batch converted signal after transmission with respect to the frequency spectrum of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission based on the delay detection time waveform An FM batch conversion signal quality estimation device, further comprising a leakage amount estimation unit.

  Further, the present invention provides a shift between a zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation step and a zero cross time of the FM batch conversion signal before and after transmission estimated by the zero cross time offset estimation step. A delay detection time waveform estimation step for estimating a delay detection time waveform of the FM batch conversion signal after transmission based on the amount of the FM batch conversion signal after transmission estimated by the delay detection time waveform estimation step. A frequency spectrum for estimating a leak amount of the frequency spectrum of the FM batch converted signal after transmission with respect to the frequency spectrum of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission based on the delay detection time waveform The FM batch conversion signal quality estimation method further comprising a leakage amount estimation step.

  According to this configuration, it is possible to estimate not only the shift amount of the zero cross time of the FM batch conversion signal before and after transmission but also the CNR related to self-phase modulation and chromatic dispersion.

  The present invention also provides an optical amplification noise amount estimation unit that estimates an amount of noise accumulated by an optical amplification device connected to the optical transmission system for the FM batch conversion signal being transmitted, and the frequency spectrum leakage A leakage amount of the frequency spectrum of the FM batch conversion signal after transmission estimated by the amount estimation unit, and a noise amount accumulated for the FM batch conversion signal during transmission estimated by the optical amplification noise amount estimation unit; An FM demodulated signal quality estimation unit for estimating the quality of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission based on the FM demodulated signal Device.

  The present invention also provides an optical amplification noise amount estimation step for estimating an amount of noise accumulated by an optical amplification device connected to the optical transmission system for the FM batch conversion signal being transmitted, and the frequency spectrum leakage A leakage amount of the frequency spectrum of the FM batch conversion signal after transmission estimated by the amount estimation step, and a noise amount accumulated for the FM batch conversion signal during transmission estimated by the optical amplification noise amount estimation step; And FM demodulated signal quality estimation step for estimating the quality of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission. Is the method.

  According to this configuration, it is possible to estimate not only CNR related to self-phase modulation and chromatic dispersion but also CNR related to all elements of the optical transmission system including optical amplification noise.

  The present invention is also an FM batch conversion signal quality estimation program for causing a computer to execute the FM batch conversion signal quality estimation method described above.

  According to this configuration, it is possible to provide a program that exhibits the effects described above.

  As described above, the present invention estimates the quality of the FM batch conversion signal at a low cost and within a realistic time even when the FM carrier conversion scheme transmission carrier plan is changed in the optical transmission system being provided. Technology can be provided.

It is a block diagram which shows the structure of the FM batch conversion signal quality estimation apparatus of this invention. It is a flowchart which shows the process of the FM batch conversion signal quality estimation method of this invention. It is a figure which shows the frequency dependence of Duty ratio of the unmodulated sine wave signal after transmission. It is a figure which shows the time waveform of the FM batch conversion signal before transmission. It is a figure which shows the instantaneous frequency of the FM batch conversion signal before transmission. It is a figure which shows the deviation | shift amount of the zero crossing time of FM batch conversion signal before and behind transmission. It is a figure which shows the deviation | shift amount of the delay detection time waveform of the FM batch conversion signal before and behind a shift. It is a figure which shows the frequency spectrum of the FM demodulated signal after transmission.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments.

(Outline of the present invention)
First, the frequency dependency D (f) of the duty ratio of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal is estimated, and the FM batch conversion signal before transmission instantaneously at the zero crossing time T _0. After calculating the sign of the frequency f (T ₀ ) and the slope a (T ₀ ), based on these estimated values and calculated values, the shift amount dT (T of the zero-cross time T ₀ of the FM batch conversion signal before and after transmission is calculated. ₀ ). Next, CNR _Duty related to self-phase modulation and chromatic dispersion is estimated. Next, CNR _Total relating to all elements of the optical transmission system including optical amplification noise is estimated.

  A block diagram showing the configuration of the FM batch conversion signal quality estimation apparatus of the present invention is shown in FIG. A flowchart showing the processing of the FM batch conversion signal quality estimation method of the present invention is shown in FIG.

  The FM batch conversion signal quality estimation device F includes an unmodulated signal estimation unit 1, an FM signal calculation unit 2, a zero-cross time lag estimation unit 3, a delay detection time waveform estimation unit 4, a frequency spectrum leakage amount estimation unit 5, an optical amplification noise. It comprises a quantity estimation unit 6 and an FM demodulated signal quality estimation unit 7.

  The FM batch conversion signal quality estimation process includes: a non-modulation signal estimation step S1, an FM signal calculation step S2, a zero cross time lag estimation step S3, a delay detection time waveform estimation step S4, a frequency spectrum leakage amount estimation step S5, and an optical amplification noise amount. It comprises an estimation step S6 and an FM demodulated signal quality estimation step S7.

  The unmodulated signal estimation step S1, the FM signal calculation step S2, and the optical amplification noise amount estimation step S6 are performed independently, and the order is not limited. The zero-cross time lag estimation step S3, the delay detection time waveform estimation step S4, the frequency spectrum leakage amount estimation step S5, and the FM demodulated signal quality estimation step S7 are each performed after the premise steps.

  In order to cause the FM batch conversion signal quality estimation apparatus F shown in FIG. 1 to execute the FM batch conversion signal quality estimation method shown in FIG. 2, the FM batch conversion signal quality estimation program is transmitted via a network or a storage medium. It is also possible to provide / acquire.

(Unmodulated signal estimation processing)
The unmodulated signal estimation unit 1 estimates the frequency dependence D (f) of the duty ratio of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal (see S1). FIG. 3 shows the frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission.

  The unmodulated signal estimation unit 1 receives parameters such as a transmission distance, the number of stages of an optical amplification device, an optical signal intensity, an optical fiber nonlinear constant, and chromatic dispersion as parameters of an optical transmission system related to self-phase modulation and chromatic dispersion. . The unmodulated signal estimation unit 1 solves the non-modulated sine after transmission by solving the nonlinear Schrodinger equation by numerical calculation for the time waveform of the unmodulated sine wave signal before transmission within the use band of the FM batch conversion signal. Find the time waveform of the wave signal. Further, the unmodulated signal estimation unit 1 estimates the duty ratio for the time waveform of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal.

  In FIG. 3, a 50 km × 4 stage optical transmission system is assumed. The frequency dependence D (f) of the duty ratio of the unmodulated sine wave signal after transmission at frequencies 1, 2, 3, 4, 5, 6 GHz of the unmodulated sine wave signal around the frequency 3 GHz of the FM carrier signal. ). Further, interpolation processing of D (f) is performed using a quadratic approximate curve.

(FM signal calculation processing)
The FM signal calculation unit 2 includes a zero-crossing time T ₀ of the FM batch conversion signal before transmission, an instantaneous frequency f (T ₀ ) at the zero-crossing time T ₀ of the FM batch conversion signal before transmission, and an FM batch conversion before transmission. The sign of the slope a (T ₀ ) at the zero crossing time T ₀ of the signal is calculated (see S2). The time waveform and instantaneous frequency of the FM batch conversion signal before transmission are shown in FIGS.

  The FM signal calculation unit 2 receives parameters such as the frequency of the FM carrier signal, the frequency of the transmission carrier signal that modulates the FM carrier signal, and the frequency shift amount as parameters of the FM batch conversion signal. Then, the FM signal calculation unit 2 calculates the time waveform S (t) of the FM batch conversion signal before transmission based on Equation 1. Further, the FM signal calculation unit 2 calculates the instantaneous frequency f (t) of the FM batch conversion signal before transmission based on Equation 2.

ここで、数式１、２の文字の定義は、以下の通りである。
Ａ：ＦＭ一括変換信号の最大振幅
ｆ_ｃ：ＦＭ搬送波信号の周波数
ｆ_ｉ：ｉ番目の伝送キャリア信号の周波数
ΔＦ_ｉ：ｉ番目の伝送キャリア信号の最大周波数偏移
φ_ｉ：ｉ番目の伝送キャリア信号の初期位相

Here, the definitions of the characters in Equations 1 and 2 are as follows.
A: Maximum amplitude of FM batch conversion signal f _c : Frequency of FM carrier signal f _i : Frequency of i-th transmission carrier signal ΔF _i : Maximum frequency shift of i-th transmission carrier signal φ _i : i-th transmission carrier Initial phase of signal

Therefore, the FM signal calculation unit 2 determines the zero cross time T ₀ of the FM batch conversion signal before transmission and the zero cross of the FM batch conversion signal before transmission based on the time waveform S (t) of the FM batch conversion signal before transmission. The sign of the slope a (T ₀ ) at time T ₀ can be estimated. Then, the FM signal calculation unit 2 estimates the instantaneous frequency f (T ₀ ) at the zero crossing time T ₀ of the FM batch conversion signal before transmission based on the instantaneous frequency f (t) of the FM batch conversion signal before transmission. Is possible.

(Zero cross time lag estimation processing)
Zero-crossing time shift amount estimate section 3, frequency-dependent D of Duty ratio of the non-modulation sine wave signal after transmission and (f), the instantaneous frequency f (T ₀ at a zero-crossing point time T ₀ of the FM batch conversion signal before transmission ), a sign of the slope a _{(T 0)} at the zero-crossing time _{T 0} before the FM batch conversion signal transmission, based on the shift amount dT _{(T 0} of the zero-cross time _{T 0} of the FM batch conversion signals before and after transmission ) Is estimated (see S3). FIG. 6 shows the shift amount of the zero cross time of the FM batch conversion signal before and after transmission.

Zero-crossing time shift amount estimate section 3, frequency-dependent D of Duty ratio of the non-modulation sine wave signal after transmission and (f), the instantaneous frequency f (T ₀ at a zero-crossing point time T ₀ of the FM batch conversion signal before transmission ) And the duty ratio D (f (T ₀ )) at the instantaneous frequency f (T ₀ ) is estimated (see FIG. 3). Then, the zero-cross time shift estimation unit 3 estimates the absolute value of the shift amount dT (T ₀ ) at the zero-cross time T ₀ of the FM batch conversion signal before and after transmission based on Equation 3. Further, the zero-cross time shift estimation unit 3 estimates the shift direction of the shift amount dT (T ₀ ) at the zero-cross time T ₀ of the FM batch conversion signal before and after transmission based on Equation 4.

ここで、ｓｇｎは、正、０、負の引数に応じ、それぞれ、＋１、０、−１の出力を行う。

Here, sgn outputs +1, 0, and −1 according to positive, zero, and negative arguments, respectively.

In FIG. 6, the time waveform S (t) of the FM batch conversion signal before and after transmission is indicated by a dotted line and a broken line, respectively. Since the sign of the slope a (T ₀ (n)) at the nth zero-crossing time T ₀ (n) of the FM batch conversion signal before transmission is positive, the nth of the FM batch conversion signal before and after transmission is positive. The shift amount dT (T ₀ (n)) at the zero crossing time T ₀ (n) is in the positive direction. On the other hand, since the sign of the slope a (T ₀ (n + 1)) at the (n + 1) -th zero-cross time T ₀ (n + 1) of the FM batch conversion signal before transmission is negative, the FM batch conversion signal before and after transmission is The shift amount dT (T ₀ (n + 1)) at the (n + 1) th zero crossing time T ₀ (n + 1) is in the negative direction.

In this way, by estimating the shift amount dT (T ₀ ) of the zero-crossing time T ₀ of the FM batch conversion signal before and after transmission, the time of the FM batch conversion signal before and after transmission due to the combined effect of self-phase modulation and chromatic dispersion. The waveform distortion quality in the time axis direction in the waveform S (t) can be estimated.

(Delay detection time waveform estimation processing)
The delay detection time waveform estimation unit 4 performs transmission based on the zero-cross time T ₀ of the FM batch conversion signal before transmission and the shift amount dT (T ₀ ) between the zero-cross time T ₀ of the FM batch conversion signal before and after transmission. The delay detection time waveform Vdemod_shift (t) of the subsequent FM batch conversion signal is estimated (see S4). FIG. 7 shows the shift amount of the delay detection time waveform of the FM batch conversion signal before and after the shift.

The delay detection time waveform estimation unit 4 calculates a delay detection time waveform Vdemod (t) that outputs a pulse having a constant width and a constant height at the zero crossing time T ₀ of the rising and falling of the FM batch conversion signal before transmission. . The delay detection time waveform estimator 4 outputs a delay detection time for outputting a pulse having a constant width and a constant height at the zero-cross time T ₀ ± dT (T ₀ ) of the rising and falling of the FM batch conversion signal after transmission. Estimate the waveform Vdemod_shift (t). Here, the pulse generation frequency corresponds to the frequency of the FM batch conversion signal.

In FIG. 7, the delay detection time waveforms Vdemod (t) and Vdemod_shift (t) of the FM batch conversion signal before and after transmission are indicated by a solid line and a broken line, respectively. Since the shift amount dT (T ₀ (n)) of the nth zero-crossing time T ₀ (n) of the FM batch conversion signal before and after transmission is in the positive direction, the nth of the FM batch conversion signal before transmission is Around the zero crossing time T ₀ (n), Vdemod_shift (t) is obtained by shifting Vdemod (t) in the positive direction. On the other hand, since the shift amount dT (T ₀ (n + 1)) of the (n + 1) -th zero-crossing time T ₀ (n + 1) of the FM batch conversion signal before and after transmission is in the negative direction, the FM batch conversion signal before transmission Around the (n + 1) th zero crossing time T ₀ (n + 1), Vdemod_shift (t) is obtained by shifting Vdemod (t) in the negative direction.

Thus, by estimating the shift amount dT (T ₀ ) of the zero-crossing time T ₀ of the FM batch conversion signal before and after transmission, the delay of the FM batch conversion signal before and after transmission due to the combined effect of self-phase modulation and chromatic dispersion. The waveform distortion quality in the time axis direction in the detection time waveform can be estimated.

(Frequency spectrum leakage estimation processing)
The frequency spectrum leakage amount estimation unit 5 applies a frequency spectrum of the FM demodulated signal generated by FM demodulation from the FM batch conversion signal after transmission based on the delay detection time waveform Vdemod_shift (t) of the FM batch conversion signal after transmission. Then, the leakage amount of the frequency spectrum of the FM batch conversion signal after transmission is estimated, and the CNR _duty related to self-phase modulation and chromatic dispersion is estimated (see S5). The frequency spectrum of the FM demodulated signal after transmission is shown in FIG.

The frequency spectrum leakage amount estimation unit 5 converts the delayed detection time waveform Vdemod_shift (t) of the FM batch conversion signal after transmission into the frequency spectrum of the FM demodulated signal after transmission using fast Fourier transform. Then, the frequency spectrum leakage amount estimation unit 5 calculates the CNR _duty related to self-phase modulation and chromatic dispersion based on the leakage amount of the frequency spectrum of the FM batch conversion signal after transmission with respect to the frequency spectrum of the FM demodulated signal after transmission. presume.

In FIG. 8, a 50 km × 4 stage optical transmission system is assumed, and the frequency of the FM carrier signal is 3 GHz. Here, delayed detection of outputting a pulse is performed at both the zero crossing time T ₀ of the rising edge and falling edge of the FM batch conversion signal. Therefore, although it is necessary to perform two types of delay detection in parallel, the frequency spectrum of the FM batch conversion signal is apparently centered on 6 GHz, and is difficult to leak into the frequency spectrum of the FM demodulated signal. Of course, delayed detection for outputting a pulse may be performed at zero crossing time T ₀ of one of rising and falling of the FM batch conversion signal. Then, the frequency spectrum of the FM batch conversion signal is centered on 3 GHz as it is, and it is easy to leak into the frequency spectrum of the FM demodulated signal, but it is sufficient to perform one kind of delayed detection alone.

(Optical amplification noise amount estimation processing)
The optical amplification noise amount estimation unit 6 estimates the noise amount accumulated by the optical amplification device connected to the optical transmission system for the FM batch conversion signal being transmitted, and estimates the CNR _RIN related to the optical amplification noise amount (Refer to S6). Although there is description also in patent document 1, it demonstrates also in this application.

The optical amplification noise amount estimation unit 6 receives the parameters of the optical transmission system related to the optical amplification noise (see Equations 5 to 8). Then, the optical amplification noise amount estimation unit 6 estimates CNR _RIN related to the optical amplification noise amount based on Equations 5 to 8.

ここで、数式５の文字の定義は、以下の通りである。
Ｐ_ｉｎ：光増幅装置への入力光電力（ｍＷ）
ＲＩＮ_ｉｎ：光増幅装置への入力光信号の相対強度雑音（Ｈｚ^−１）
ＲＩＮ_ｏｕｔ：光増幅装置からの出力光信号の相対強度雑音（Ｈｚ^−１）
ＮＦ：光増幅雑音指数
Ｅ：光子エネルギー（１．２７８×１０^−１９Ｊ）
光増幅装置を多段接続する場合には、数式５の計算を接続段数分繰り返し、最遠端の光増幅装置からの出力光信号の相対強度雑音ＲＩＮ_ｏｕｔを計算する。

Here, the definition of the character of Formula 5 is as follows.
P _in: input optical power to the optical amplifier (mW)
RIN _in : Relative intensity noise (Hz ⁻¹ ) of the optical signal input to the optical amplifier
RIN _out : Relative intensity noise (Hz ⁻¹ ) of the output optical signal from the optical amplifier
NF: optical amplification noise figure E: photon energy (1.278 × 10 ⁻¹⁹ J)
When optical amplifiers are connected in multiple stages, the calculation of Equation 5 is repeated for the number of connected stages, and the relative intensity noise RIN _out of the output optical signal from the farthest end optical amplifier is calculated.

ここで、数式６の文字の定義は、以下の通りである。
ｆ：キャリア周波数（ＭＨｚ）
ΔＦ（ｆ）：周波数偏移量（ＭＨｚ_０−ｐ／ｃｈ）
Ｂ_Ｎ：雑音帯域幅（ＭＨｚ）

Here, the definition of the character of Formula 6 is as follows.
f: Carrier frequency (MHz)
ΔF (f): Frequency deviation (MHz _0-p / ch)
B _N : Noise bandwidth (MHz)

ここで、数式７の文字の定義は、以下の通りである。
ＣＮＲ_{ｐｈａｓｅ}（ｆ）＝Δν・１０^６／２πｆ^２
Δν：ビート線幅（Ｈｚ）
ＣＮＲ_{ｈｅｔｅｒｏｄｙｎｅ}：ＦＭ伝送区間の雑音

Here, the definition of the character of Formula 7 is as follows.
CNR _phase (f) = Δν · 10 ⁶ / 2πf ²
Δν: Beat line width (Hz)
CNR _heterodyne : FM transmission section noise

ここで、数式８の文字の定義は、以下の通りである。
ｍ：ＯＮＵへの入力信号光の光変調度
Ｒ：受光素子のＯ／Ｅ変換効率（Ａ／Ｗ）
Ｐ_ｒ：受光電力（Ｗ）
ＲＩＮ：ＯＮＵへの入力信号光の相対強度雑音（ｄＢ／Ｈｚ）
ｅ：電気素量（１．６０２×１０^−１９Ｃ）
Ｉ_ｄ０：受光素子の暗電流（ｎＡ）
Ｎ_Ｆ：受光素子の入力換算雑音（ｐＡ／Ｈｚ^１／２）
光増幅装置を多段接続する場合には、ＯＮＵへの入力信号光の相対強度雑音ＲＩＮは、最遠端の光増幅装置からの出力光信号の相対強度雑音ＲＩＮ_ｏｕｔに等しい。

Here, the definition of the character of Formula 8 is as follows.
m: degree of optical modulation of input signal light to ONU R: O / E conversion efficiency (A / W) of light receiving element
P _r : received light power (W)
RIN: Relative intensity noise of input signal light to ONU (dB / Hz)
e: Elementary electric quantity (1.602 × 10 ⁻¹⁹ C)
I _d0 : dark current of the light receiving element (nA)
N _F : Input conversion noise of the light receiving element (pA / Hz ^1/2 )
When optical amplifiers are connected in multiple stages, the relative intensity noise RIN of the input signal light to the ONU is equal to the relative intensity noise RIN _out of the output optical signal from the farthest end optical amplifier.

(FM demodulated signal quality estimation processing)
The FM demodulated signal quality estimator 7 calculates the FM batch after transmission based on the leakage amount of the frequency spectrum of the FM batch conversion signal after transmission and the noise amount accumulated for the FM batch conversion signal during transmission. The quality CNR _Total of the FM demodulated signal generated by FM demodulation from the converted signal is estimated (see S7). Here, the leakage amount of the frequency spectrum of the FM batch conversion signal after transmission corresponds to CNR _Duty related to self-phase modulation and chromatic dispersion. The amount of noise accumulated for the FM batch conversion signal being transmitted corresponds to CNR _RIN related to the amount of optical amplification noise.

The FM demodulated signal quality estimator 7 adds the CNR _Duty related to self-phase modulation and chromatic dispersion and the CNR _RIN related to the amount of optical amplification noise in terms of power based on Equation 9 to obtain FM after transmission. The quality CNR _{Total of the} demodulated signal is estimated.

(Effect of the present invention)
Thus, it is not necessary to “measure in advance” the dependency of CNR _Duty related to self-phase modulation and chromatic dispersion on the duty ratio of the unmodulated FM carrier signal after transmission. For the time waveform of the unmodulated sine wave signal before transmission, it is sufficient to obtain the time waveform of the unmodulated sine wave signal after transmission by solving the nonlinear Schrodinger equation by numerical calculation.

Furthermore, not only the shift amount dT (T ₀ ) of the zero-crossing time T ₀ of the FM batch conversion signal before and after transmission but also all elements of the optical transmission system including CNR _Duty and optical amplification noise related to self-phase modulation and chromatic dispersion. CNR _Total can be estimated. Therefore, it is possible to provide a technique for estimating the quality of an FM demodulated signal at a low cost and within a practical time even when an FM batch conversion scheme transmission carrier plan is changed in a provided optical transmission system. it can.

  The FM batch conversion signal quality estimation apparatus, method, and program of the present invention can be applied to an optical video distribution system using the FM batch conversion method.

F: FM batch conversion signal quality estimation device 1: Unmodulated signal estimation unit 2: FM signal calculation unit 3: Zero-cross time lag estimation unit 4: Delay detection time waveform estimation unit 5: Frequency spectrum leakage amount estimation unit 6: Optical amplification Noise amount estimation unit 7: FM demodulated signal quality estimation unit

Claims (7)

An FM batch conversion signal quality estimation device for estimating the quality of the FM batch conversion signal after the FM batch conversion signal is transmitted by an optical transmission system,
An unmodulated signal estimator for estimating the frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal;
Calculates the zero-cross time of the FM batch conversion signal before transmission, the instantaneous frequency at the zero-cross time of the FM batch conversion signal before transmission, and the sign of the slope at the zero-cross time of the FM batch conversion signal before transmission An FM signal calculator to
The frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission estimated by the unmodulated signal estimation unit and the instantaneous frequency at the zero-crossing time of the FM batch conversion signal before transmission calculated by the FM signal calculation unit And the zero cross time that estimates the deviation amount of the zero batch time of the FM batch conversion signal before and after transmission based on the sign of the slope at the zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation unit A time lag estimation unit;
An FM batch conversion signal quality estimation apparatus comprising: Based on the zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation unit and the shift amount of the zero cross time of the FM batch conversion signal before and after transmission estimated by the zero cross time shift estimation unit. A delay detection time waveform estimation unit for estimating a delay detection time waveform of the FM batch conversion signal after transmission;
Based on the delayed detection time waveform of the FM batch conversion signal after transmission estimated by the delay detection time waveform estimation unit, with respect to the frequency spectrum of the FM demodulated signal generated by FM demodulation from the FM batch conversion signal after transmission, A frequency spectrum leakage amount estimation unit for estimating a frequency spectrum leakage amount of the FM batch conversion signal after transmission;
The FM batch conversion signal quality estimation apparatus according to claim 1, further comprising: An optical amplification noise amount estimation unit that estimates an amount of noise accumulated by an optical amplification device connected to the optical transmission system with respect to the FM batch conversion signal being transmitted;
The frequency spectrum leakage amount of the FM batch conversion signal after transmission estimated by the frequency spectrum leakage amount estimation unit and the FM batch conversion signal being transmitted estimated by the optical amplification noise amount estimation unit are stored. An FM demodulated signal quality estimation unit that estimates the quality of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission based on the amount of noise;
The FM batch conversion signal quality estimation apparatus according to claim 2, further comprising: An FM batch conversion signal quality estimation method for estimating the quality of the FM batch conversion signal after the FM batch conversion signal is transmitted by an optical transmission system,
An unmodulated signal estimation step of estimating the frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission within the use band of the FM batch conversion signal;
Calculates the zero-cross time of the FM batch conversion signal before transmission, the instantaneous frequency at the zero-cross time of the FM batch conversion signal before transmission, and the sign of the slope at the zero-cross time of the FM batch conversion signal before transmission FM signal calculation step to perform,
The frequency dependence of the duty ratio of the unmodulated sine wave signal after transmission estimated by the unmodulated signal estimation step and the instantaneous frequency at the zero crossing time of the FM batch conversion signal before transmission calculated by the FM signal calculation step And the zero cross time for estimating the shift amount of the FM batch conversion signal before and after transmission based on the sign of the slope at the zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation step. A time lag estimation step;
An FM batch conversion signal quality estimation method comprising: Based on the zero cross time of the FM batch conversion signal before transmission calculated by the FM signal calculation step and the shift amount of the zero cross time of the FM batch conversion signal before and after transmission estimated by the zero cross time shift estimation step. A delay detection time waveform estimation step for estimating a delay detection time waveform of the FM batch conversion signal after transmission;
Based on the delay detection time waveform of the FM batch conversion signal after transmission estimated by the delay detection time waveform estimation step, with respect to the frequency spectrum of the FM demodulated signal generated by FM demodulation from the FM batch conversion signal after transmission, A frequency spectrum leakage amount estimation step for estimating a leakage amount of the frequency spectrum of the FM batch conversion signal after transmission;
The FM batch conversion signal quality estimation method according to claim 4, further comprising: An optical amplification noise amount estimation step for estimating an amount of noise accumulated by an optical amplification device connected to the optical transmission system with respect to the FM batch conversion signal being transmitted;
The frequency spectrum leakage amount of the FM batch conversion signal after transmission estimated by the frequency spectrum leakage amount estimation step and the FM batch conversion signal during transmission estimated by the optical amplification noise amount estimation step are stored. An FM demodulated signal quality estimation step for estimating the quality of the FM demodulated signal generated by FM demodulation from the FM batch converted signal after transmission based on the amount of noise;
The FM batch conversion signal quality estimation method according to claim 5, further comprising:   An FM batch conversion signal quality estimation program for causing a computer to execute the FM batch conversion signal quality estimation method according to claim 4.

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