JP6386369B2 - Optical signal receiving apparatus and optical signal receiving method - Google Patents

Description

  The present invention relates to an optical signal receiving apparatus and an optical signal receiving method for receiving an optical signal transmitted through an optical fiber transmission line using a digital coherent detection technique.

  In an ultra-high-speed transmission system having a transmission rate per channel of 100 Gbit / s or more, a digital coherent technology combining a coherent optical communication technology and a digital signal processing technology is widely used. For example, in a DP-QPSK (Dual Polarization-Quadrature Phase Shift Keying) method (for example, see Non-Patent Document 1), which is a standard modulation / demodulation method in a 100 Gbit / s long-distance optical transmission system, quaternary phase modulation is used. As a result, a signal having a symbol rate of 32 Gbit / s is multiplexed twice to generate a coherent optical signal, and further multiplexed using two polarizations to generate a 128 Gbit / s coherent optical signal. On the receiving side, the signal coherently received using local light of the same wavelength as the signal light is digitized using an AD (Analog to Digital) converter and then subjected to chromatic dispersion compensation and polarization of the transmission path by digital signal processing. Excellent transmission characteristics are realized by performing dispersion compensation, polarization signal separation, frequency offset compensation, carrier phase compensation, and the like.

  In recent years, in order to realize a transmission rate exceeding 100 Gbit / s per channel, an optical multicarrier transmission scheme in which a plurality of subcarrier signals are multiplexed and transmitted as one channel has been studied. For example, in Non-Patent Document 2, transmission of 1 Tbit / s per channel is realized by transmitting and receiving 349 Git / s DP-32QAM (Quadrature Amplitude Modulation) subcarrier signals in parallel in three waves.

  Further, in the optical signal receiver using the digital coherent detection technique, the chromatic dispersion generated in the optical signal transmitted through the optical fiber transmission line is compensated by the chromatic dispersion compensation circuit of the digital signal processing apparatus. In a chromatic dispersion compensation circuit, for example, light generated by chromatic dispersion using a chromatic dispersion amount measured in advance by a chromatic dispersion measuring device or a chromatic dispersion amount estimated by a chromatic dispersion estimating circuit mounted on a digital signal processing device. Compensates for signal waveform distortion. There is also a method for estimating and compensating for chromatic dispersion by adaptively controlling the chromatic dispersion compensation circuit.

  Furthermore, in the chromatic dispersion compensation circuit, when the chromatic dispersion value measured in advance by the chromatic dispersion measuring device is used, it is impossible to follow the variation of the chromatic dispersion amount caused by the environmental variation, so that the characteristics of the received signal are deteriorated. In a method of estimating a chromatic dispersion value using a chromatic dispersion estimation circuit mounted on a digital signal processing apparatus (see, for example, Non-Patent Document 3), a pilot signal is added to a data signal, and thus the signal data rate increases.

OIF, “100G Ultra Long Haul DWDM Framework Document”. J. Renaudier, R. Rios Muller, L. Schmalen, P. Tran, P. Brindel and G. Charlet, “1-Tb / s PDM-32QAM Superchannel Transmission at 6.7-b / s / Hz over SSMF and 150-GHz -Grid ROADMs, ”ECOC2014, Tu.3.3.4, Cannes, France, 2012. K. Ishihara, E. Yamazaki, T. Nakagawa, R. Kudo, T. Kobayashi and Y. Miyamoto, “Fast chromatic dispersion estimation for coherent optical transmission systems,” Electronics Letters, vol. 48, no. 20, pp. 1290 -1292, 2012.

  As described above, the method for estimating and compensating for chromatic dispersion by adaptively controlling the chromatic dispersion compensation circuit has a problem in that the circuit scale of the digital signal processing apparatus is increased by adaptive control. Further, the above-described chromatic dispersion estimation / compensation method has a problem in that the accuracy of chromatic dispersion estimation is lowered under a severe optical signal to noise ratio (OSNR) in the optical transmission line. .

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical signal receiving apparatus and an optical signal receiving method capable of estimating a chromatic dispersion amount easily and with high accuracy.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving apparatus including a carrier signal receiver, wherein the digital signal is input and a frame signal is output, and a digital signal processing unit that inputs the output frame signal and performs frame signal processing to obtain a client signal. Client signal output means for outputting, delay amount output means for outputting the bit delay amount between the subcarrier signals from the frame signal, and chromatic dispersion for calculating the chromatic dispersion amount of the optical fiber transmission line using the bit delay amount And a quantity calculating means.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving apparatus including a carrier signal receiver, wherein the digital signal is input, the frame signal is output, and the symbol signal of the subcarrier signal is output, and the output frame signal A client signal output means for outputting a client signal by performing frame signal processing, a delay time output means for outputting a delay time generated between the subcarrier signals based on the frame signal and the symbol rate, and the delay Chromatic dispersion amount calculating means for calculating the chromatic dispersion amount of the optical fiber transmission line using time And wherein the door.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving device including a carrier signal receiver, wherein the digital signal is input, the frame signal is output, and the digital signal that outputs the symbol rate of the subcarrier signal and the center wavelength of the subcarrier signal Processing means; client signal output means for inputting the output frame signal, processing the frame signal to output a client signal; and delay amount output means for outputting a bit delay amount between the subcarrier signals from the frame signal; The optical signal is transmitted using the bit delay amount between the frame signals, the symbol rate, and the center wavelength. Characterized in that a wavelength dispersion value calculating means for calculating the chromatic dispersion of Iba transmission path.

  The present invention is characterized by further comprising dispersion compensation means for compensating the chromatic dispersion of the optical fiber transmission line based on the chromatic dispersion amount.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving method performed by an optical signal receiving apparatus including a carrier signal receiver, wherein the digital signal is input and a frame signal is output, and the output frame signal is input and the frame signal is input. A client signal output step of processing and outputting a client signal; a delay amount output step of outputting a bit delay amount between the subcarrier signals from the frame signal; and a chromatic dispersion of the optical fiber transmission line using the bit delay amount And a chromatic dispersion amount calculating step for calculating the amount.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving method performed by an optical signal receiving device including a carrier signal receiver, wherein the digital signal is input, the frame signal is output, and the symbol rate of the subcarrier signal is output, A client signal output step for inputting the output frame signal, processing the frame signal and outputting a client signal, and a delay time for outputting a delay time generated between the subcarrier signals based on the frame signal and the symbol rate Calculate the chromatic dispersion amount of the optical fiber transmission line using the output step and the delay time. And having a wavelength dispersion amount calculation step that.

  The present invention divides an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) wave subcarrier signals, and outputs a digital signal from the N wave subcarrier signals. An optical signal receiving method performed by an optical signal receiving apparatus including a carrier signal receiver, wherein the digital signal is input, a frame signal is output, a symbol rate of the subcarrier signal, and a center wavelength of the subcarrier signal A digital signal processing step for outputting the frame signal, a client signal output step for inputting the output frame signal, processing the frame signal to output a client signal, and outputting a bit delay amount between the subcarrier signals from the frame signal A delay amount output step, a bit delay amount between the frame signals, and the symbol rate And having a wavelength dispersion amount calculation step of calculating the chromatic dispersion of the optical fiber transmission line with said central wavelength.

  According to the present invention, the bit delay amount between the subcarrier signals constituting the optical multicarrier signal is measured, and the chromatic dispersion amount is obtained by calculation using this bit delay amount. The effect that the amount of dispersion can be estimated is obtained.

It is a block which shows the structure of the optical signal receiver by 1st Embodiment of this invention. It is a flowchart which shows the operation | movement of the optical signal received signal shown in FIG. It is a block which shows the structure of the optical signal receiver by 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of the optical signal received signal shown in FIG. It is a block which shows the structure of the optical signal receiver by 3rd Embodiment of this invention. 6 is a flowchart showing an operation of the optical signal reception signal shown in FIG. 5. It is a block which shows the structure of the optical signal receiver by 4th Embodiment of this invention. It is a flowchart which shows operation | movement of the optical signal received signal shown in FIG.

<First Embodiment>
Hereinafter, an optical signal receiving apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, an optical signal receiving apparatus 1 demultiplexes an input optical multicarrier signal into subcarrier signals E _{1 to} E _N (the number N of subcarrier signals is a positive integer larger than 1). When an optical multicarrier signal receiver 20 of the sub-carrier signals _E 1 to E _N each coherent detection and outputs the digital signal _s 1 ~s _N, waveform equalization and digital signal _s 1 ~s _N and digital signal processing become a digital signal processor 30 for demodulating a frame signal _d 1 to d _N, between the client signal c and the frame signal and a frame signal processing frame signals _d 1 _{~d N d k} and _{d l (1 ≦ k <l} ≦ N) a frame signal receiving device 40 that outputs a bit delay amount T _kl and a client signal transmitter 50 that outputs a client signal c. The digital signal processing device 30 includes a chromatic dispersion amount calculation circuit 301. The chromatic dispersion amount calculation circuit 301 calculates the chromatic dispersion amount using the bit delay amount T _kl between the frame signals d _k and d _l output from the frame signal receiving device 40. The calculated chromatic dispersion amount is used in a chromatic dispersion compensation circuit (not shown) of the digital signal processing apparatus.

An example of the frame signal is OTN (Optical Transport Network) defined by ITU-T. OTUCn of n × 100 Gbit / s (n is a positive integer larger than 1) has been studied as a frame signal that realizes transmission exceeding 100 Gbit / s (for example, see Reference 1).
Reference 1: “Takuya Ohara,“ OTN Interface Technology and Standardization Trends ”, BI-5-1, IEICE General Conference, 2014.”

For example, in the case of 400 Gbit / s transmission using 4 subcarriers, the OTUC4 signal is distributed to four 100 Gbit / s signals OTLC 4.4 # 1, OTLC 4.4 # 2, OTLC 4.4 # 3, and OTLC 4.4 # 4. Each OTLC 4.4 signal is transmitted using subcarriers. On the receiving side, OTLC 4.4 # 1, OTLC 4.4 # 2, OTLC 4.4 # 3, and OTLC 4.4 # 4 are used as outputs d ₁ , d ₂ , d ₃ , and d ₄ of the digital signal processing device 30. OTLC 4.4 # i (1 ≦ i ≦ 4 in this example) has a frame structure, and there is a FAS (Frame Alignment Signal) having a fixed bit pattern at the head of the frame, and 1 behind the FAS. There is MFAS (Multi-Frame Alignment Signal) which is a counter that increments a number from 0 to 255 for each frame.

  The frame signal receiving apparatus finds the FAS fixed bit pattern for each received OTLC 4.4 # i (1 ≦ i ≦ 4 in this example), recognizes the boundary of the frame, and then detects FAS or both FAS and MFAS. To detect the skew between OTLC4.4 # i. After deskewing using a buffer or the like based on the detected skew information, the OTUC4 signal is reproduced. The skew information corresponds to the bit delay amount between frame signals.

The relationship between the delay time Δt _kl generated between the subcarrier signals E _k and E _{l due} to chromatic dispersion and the chromatic dispersion amount D _kl L is expressed by the equation (1) (for example, see Reference 2).
Reference 2: “TE Dimmick, G. Rossi, and DJ Blumenthal,“ Optical Dispersion Monitoring Technique Using Double Sideband Subcarriers, ”IEEE Photonics Technology. Letters, vol. 12, no. 7, pp. 900-902, 2000.”

Here, f _S is the symbol rate of the subcarrier signal, Δf is the subcarrier signal interval, λ _k and λ _l are the center wavelengths of the subcarrier signals E _k and E _l , C is the speed of light, and D _kl is per unit length. The chromatic dispersion amount and L indicate the length of the optical fiber transmission line. By modifying the equation (1), the chromatic dispersion amount D _kl L can be calculated using the inter-subcarrier signal bit delay amount T _kl output from the frame signal receiving device 40. In this embodiment, since the optical multicarrier signal is composed of N-wave subcarrier signals, chromatic dispersion amounts D ₁₂ L to D _{(n−1) n} L can be calculated. The calculated chromatic dispersion amount is used in a chromatic dispersion compensation circuit (not shown) in the digital signal processing device 30.

In the present embodiment, since the chromatic dispersion amounts D ₁₂ L to D _{(n−1) n} L can be calculated, the chromatic dispersion amount of the transmission line at an arbitrary wavelength is calculated using these chromatic dispersion amounts. Is possible. For example, when transmission is performed in the 1550 nm band, the relationship between the chromatic dispersion DL and the wavelength λ is expressed by equation (2) (for example, see Reference 3).
Reference 3: “ITU-T, G.652,“ Transmission media and optical systems characteristics -Optical fiber cables ”.”
DL = L [D ₁₅₅₀ + S ₁₅₅₀ ) λ-1550)] (2)

Here, D ₁₅₅₀ represents a chromatic dispersion amount per unit length at a wavelength of 1550 nm, and S ₁₅₅₀ represents a dispersion slope. Since D ₁₅₅₀ and S ₁₅₅₀ in equation (2) can be obtained using the chromatic dispersion amount calculated in the present embodiment, the chromatic dispersion amount DL of the transmission line at an arbitrary wavelength λ can be calculated. .

Next, the operation of the optical signal receiving apparatus 1 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the optical signal receiving apparatus 1 shown in FIG. First, the wavelength demultiplexer 10 demultiplexes the input optical multicarrier signal into subcarrier signals E _{1 to} E _N (the number N of subcarrier signals is a positive integer greater than 1) (step S1). Subsequently, the optical multicarrier signal receiver 20, the demultiplexed sub-carrier signals _E 1 to E _N respectively coherent detection and outputs the digital signal _s 1 ~s _N (step S2).

Next, the digital signal processing device 30 performs digital signal processing on the digital signals s _{1 to} s _N to perform waveform equalization and demodulates them into frame signals d _{1 to} d _N (step S3). Subsequently, the frame signal receiving device 40 performs frame signal processing on the demodulated frame signals d _{1 to} d _N and outputs a client signal c (step S4). Further, the frame signal receiving device 40 obtains the bit delay amount T _kl between the frame signals d _k and d _l (1 ≦ k <l ≦ N) and outputs it to the chromatic dispersion amount calculation circuit 301 (step S5).

Next, the chromatic dispersion amount calculation circuit 301 calculates the chromatic dispersion amount using the bit delay amount T _kl between the frame signals d _k and d _l output from the frame signal receiving device 40 (step S6). The calculated chromatic dispersion amount is used by a chromatic dispersion compensation circuit (not shown) in the digital signal processing device 30. In parallel with this, the client signal transmitter 50 outputs the client signal c output from the frame signal receiving device 40 to the outside (step S7). The client signal transmitter 50 does not necessarily have to be provided in the optical signal receiving device 1. In the optical signal receiving device 1, some processing is performed on the client signal c output from the frame signal receiving device 40. May be.

Second Embodiment
Next, an optical signal receiving apparatus according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the embodiment. The optical signal receiving apparatus 1 shown in FIG. 3 shows a configuration example when the number of subcarrier signals N = 2 in the optical signal receiving apparatus 1 shown in FIG. FIG. 3 also shows an optical signal transmitter 2 used as a pair with the optical signal receiver 1.

The optical signal transmitter 2 that outputs an optical multicarrier signal includes a client signal receiver 60 that receives a client signal c, a frame signal transmitter 70 that converts the client signal c into frame signals d ₁ and d ₂ , and a frame signal. d ₁ and _{d 2,} respectively 128Gbit / s (symbol rate: 32Gbit / s) sub-carrier transmitter 80 DP-QPSK subcarrier signals _{E 1} and modulates the _{E 2} output, the sub-carrier transmitter 90, sub It is composed of a wavelength multiplexer 100 that combines the carrier signals E ₁ and E ₂ and outputs the result as an optical multicarrier signal of 256 Gbit / s to the optical fiber transmission line 3 configured of a single mode fiber 240 km. .

An optical receiver 1 that receives an optical multicarrier signal transmitted through an optical fiber transmission line has a wavelength component that demultiplexes a 256 Gbit / s optical multicarrier signal into subcarrier signals E ₁ and E ₂ of 128 Gbit / s DP-QPSK. The optical wave carrier 10, the optical multicarrier signal receiver 20 that outputs the digital signals s ₁ and s ₂ by coherent detection of the subcarrier signals E ₁ and E ₂ , respectively, and the digital signals s ₁ and s ₂ are subjected to digital signal processing. Te and digital signal processor 31 for demodulating a frame signal _{d 1} and _{d 2,} the bit delay amount _{T 12} between the frame signals _{d 1} and _{d 2} are treated frame signal client signal c and the frame signals _{d 1} and _{d 2} It consists of a frame signal receiving device 40 for outputting and a client signal transmitter for outputting the client signal c to the outside. ing.

Next, the configuration of the digital signal processing device 31 shown in FIG. 3 will be described. Digital signal processing device in the optical signal receiving apparatus 1 shown in FIG. 3. 31, the wavelength dispersion of calculating the amount of chromatic dispersion using a bit delay amount T ₁₂ between the frame signals d ₁ and d ₂ of the frame signal receiving apparatus 40 outputs amount calculation circuit 310, a chromatic dispersion compensation circuit 311 that compensates for wavelength dispersion of the digital signal _{s 1} and _{s 2,} corresponding to the sub-carrier signals _{E 1} and _{E 2,} adaptive equalizer for performing waveform equalization and polarization separation Circuit 313, 314, carrier phase compensation circuit 315, 316 for estimating and compensating for frequency offset and phase noise, and demodulation for demodulating digital signal processed digital signals s ₁ and s ₂ into frame signals d ₁ and d ₂ And circuits 317 and 318.

Next, the operation of the optical signal receiving apparatus 1 shown in FIG. 3 will be described with reference to FIG. FIG. 4 is a flowchart showing the operation of the optical signal receiving apparatus 1 shown in FIG. First, the wavelength demultiplexer 10 demultiplexes the input optical multicarrier signal into subcarrier signals E _{1 to} E _N (the number N of subcarrier signals is a positive integer greater than 1) (step S12). Subsequently, the optical multicarrier signal receiver 20, the demultiplexed sub-carrier signals _E 1 to E _N respectively coherent detection and outputs the digital signal _s 1 ~s _N (step S12).

Then, the digital signal processor 30 demodulates the frame signal _d 1 to d _N of the digital signal _s 1 ~s _N and digital signal processing (step S13). Subsequently, the frame signal receiving device 40 performs frame signal processing on the demodulated frame signals d _{1 to} d _N and outputs a client signal c (step S14). The frame signal receiving apparatus 40 outputs the frame signal _{d k} and _{d l} between (1 ≦ k <l ≦ N ) Wavelength dispersion amount calculation circuit 310 obtains the bit delay amount _{T 12} of (step S15).

  In parallel with this, the client signal transmitter 50 outputs the client signal c output from the frame signal receiving device 40 to the outside (step S16).

Next, a detailed processing operation of the digital signal processing device 31 will be described. Wavelength dispersion amount calculation circuit 310 calculates the amount of chromatic dispersion of between subcarriers bit delay _{T 12} (step S131). The chromatic dispersion compensation circuits 311 and 312 compensate the chromatic dispersion using the calculated chromatic dispersion amount D ₁₂ L (step S132).

Next, the adaptive equalization circuits 313 and 314 perform waveform equalization and polarization separation (step S133). Subsequently, the carrier phase compensation circuits 315 and 316 are estimated and compensated for the frequency offset and phase noise (step S134). Then, the demodulation circuits 317 and 318 demodulate the digital signals s ₁ and s ₂ subjected to the digital signal processing into frame signals d ₁ and d ₂ (step S135).

In this embodiment, the subcarrier signal interval Δf is 37.5 GHz, and the center wavelengths of the subcarrier signals E ₁ and E ₂ are λ ₁ = 1580.194 nm and λ ₂ = 1580.507 nm, respectively. Further, in the present embodiment, the bit delay amount T ₁₂ between subcarriers frame signal receiving apparatus 40 outputs was 44 bits. The chromatic dispersion amount D ₁₂ L of the optical fiber transmission line output by the chromatic dispersion amount calculation circuit in the digital signal processing device 31 using the expression (1) is 4401.34 ps / nm. The chromatic dispersion amount D ₁₂ L of the optical fiber transmission line measured in advance by the chromatic dispersion measuring device is 4396.73 ps / nm, and the chromatic dispersion amount estimated by the chromatic dispersion amount calculation circuit in this embodiment is a close value. .

<Third Embodiment>
Next, an optical signal receiving apparatus according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the configuration of the embodiment. As in the first embodiment, the optical signal receiving device 1 shown in FIG. 5 includes a wavelength demultiplexer 10, an optical multicarrier signal receiver 20, a digital signal processing device 32, a frame signal receiving device 41, and a client. The digital signal processing device 32 includes a chromatic dispersion amount calculation circuit 318.

The digital signal processing device 32 in the optical signal receiving device 1 shown in FIG. 5 outputs the symbol rate f _S of the subcarrier signal to the frame signal receiving device 41 as the multicarrier signal information. The frame signal receiver 41 receives the symbol rate f _S input from the digital signal processor 32 and the bit delay amount T between the frame signals d _k and d _l (1 ≦ k <l ≦ N) obtained during the frame signal processing. _kl is used to calculate the delay time Δt _kl = T _kl / f _S generated between the subcarrier signals E _k and E _l by chromatic dispersion, and the inter-subcarrier delay time Δt _kl is calculated as the wavelength of the digital signal processing device 32. Input to a dispersion amount calculation circuit (not shown).

The chromatic dispersion amount calculation circuit 318 in the digital signal processing device 32 calculates the chromatic dispersion amount D _kl L using equation (1) using the inter-subcarrier delay time Δt _kl input from the frame signal receiving device 41. To do. The calculated chromatic dispersion amount is used in the chromatic dispersion compensation circuit of the digital signal processing device 32.

Next, the operation of the optical signal receiving apparatus shown in FIG. 5 will be described with reference to FIG. FIG. 6 is a flowchart showing the operation of the optical signal receiving apparatus shown in FIG. First, the wavelength demultiplexer 10 demultiplexes the input optical multicarrier signal into subcarrier signals E _{1 to} E _N (the number N of subcarrier signals is a positive integer larger than 1) (step S21). Subsequently, the optical multicarrier signal receiver 20, the demultiplexed sub-carrier signals _E 1 to E _N respectively coherent detection and outputs the digital signal _s 1 ~s _N (step S22).

Next, the digital signal processing device 30 performs digital signal processing on the digital signals s _{1 to} s _N to perform waveform equalization and demodulates them into frame signals d _{1 to} d _N (step S23). Then, the digital signal processing device 32 outputs multicarrier signal information (symbol rate F _S of the subcarrier signal) (step S24).

Next, the frame signal receiving device 41 performs frame signal processing on the demodulated frame signals d _{1 to} d _N and outputs a client signal c (step S25). The frame signal receiving device 41 also has a bit delay between the symbol rate f _S input from the digital signal processing device 32 and the frame signals d _k and d _l (1 ≦ k <l ≦ N) obtained during the frame signal processing. Using the amount T _kl , the delay time Δt _kl = T _kl / f _S generated between the subcarrier signals E _k and E _l by chromatic dispersion is output to the chromatic dispersion amount calculation circuit 318 (step S26).

Next, the chromatic dispersion amount calculation circuit 318 calculates the chromatic dispersion amount using the delay time Δt _kl output from the frame signal receiving device 40 (step S27). The calculated chromatic dispersion amount is used by a chromatic dispersion compensation circuit (not shown) in the digital signal processing device 30. In parallel with this, the client signal transmitter 50 outputs the client signal c output from the frame signal receiver 40 to the outside (step S28).

<Fourth embodiment>
Next, an optical signal receiving apparatus according to a fourth embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing the configuration of the embodiment. As in the first and third embodiments, the optical signal receiving device 1 illustrated in FIG. 7 includes a wavelength demultiplexer 10, an optical multicarrier signal receiver 20, a digital signal processing device 32, and a frame signal reception. The frame signal receiving device 42 includes a chromatic dispersion amount calculating function 420. The frame signal receiving device 42 includes a device 42 and a client signal transmitter 50.

The digital signal processing device 32 in the optical signal receiving device 1 shown in FIG. 7 outputs the symbol rate f _S and the center wavelengths λ _{1 to} λ _N of the subcarrier signal to the frame signal receiving device 42 as multicarrier signal information. The chromatic dispersion amount calculation function 420 provided in the frame signal receiving device 42 is a symbol rate f _S and center wavelengths λ _{1 to} λ _N input from the digital signal processing device 32 and any two frame signals obtained at the time of frame signal processing. Using the bit delay amount T _kl between d _k and d _l (1 ≦ k <l ≦ N), the chromatic dispersion amount D _kl L is calculated from the equation (1). The chromatic dispersion amount calculated by the chromatic dispersion amount calculation function 420 in the frame signal receiving device 42 is input to a chromatic dispersion compensation circuit (not shown) of the digital signal processing device 32.

Next, the operation of the optical signal receiving apparatus shown in FIG. 7 will be described with reference to FIG. FIG. 8 is a flowchart showing the operation of the optical signal receiving apparatus shown in FIG. First, the wavelength demultiplexer 10 demultiplexes the input optical multicarrier signal into subcarrier signals E _{1 to} E _N (the number N of subcarrier signals is a positive integer greater than 1) (step S31). Subsequently, the optical multicarrier signal receiver 20, the demultiplexed sub-carrier signals _E 1 to E _N respectively coherent detection and outputs the digital signal _s 1 ~s _N (step S32).

Next, the digital signal processing device 30 performs digital signal processing on the digital signals s _{1 to} s _N to perform waveform equalization and demodulates them into frame signals d _{1 to} d _N (step S33). The digital signal processing device 33 then outputs multicarrier signal information (subcarrier signal symbol rate f _S and center wavelengths λ _{1 to} λ _N ) (step S34).

Next, the frame signal receiving device 41 performs frame signal processing on the demodulated frame signals d _{1 to} d _N and outputs a client signal c (step S35). The frame signal receiving device 41 also has a bit delay between the symbol rate f _S input from the digital signal processing device 33 and the frame signals d _k and d _l (1 ≦ k <l ≦ N) obtained during the frame signal processing. Using the amount T _kl , the delay time Δt _kl = T _kl / f _S generated between the subcarrier signals E _k and E _l by chromatic dispersion is output to the chromatic dispersion amount calculation function 420 (step S36).

Next, the chromatic dispersion amount calculation function 420 calculates the chromatic dispersion amount using the output delay time Δt _kl (step S37). The calculated chromatic dispersion amount is used in a chromatic dispersion compensation circuit (not shown) in the digital signal processing device 33. In parallel with this, the client signal transmitter 50 outputs the client signal c output from the frame signal receiving device 40 to the outside (step S38).

  As described above, an optical multicarrier signal transmitted through an optical fiber transmission line is received by coherent detection by an optical multicarrier signal receiver, demodulated by a digital signal processor, and then received by an optical multicarrier signal in a frame signal receiver. It is possible to estimate the chromatic dispersion amount with high accuracy by measuring the bit delay amount between the subcarrier signals constituting the signal and calculating the chromatic dispersion amount using the bit delay amount.

  The optical signal receiving device in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in the computer system. It may be realized using hardware such as PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array).

  As mentioned above, although embodiment of this invention has been described with reference to drawings, the said embodiment is only the illustration of this invention, and it is clear that this invention is not limited to the said embodiment. is there. Therefore, additions, omissions, substitutions, and other modifications of the components may be made without departing from the technical idea and scope of the present invention.

  An optical multicarrier signal transmitted through an optical fiber transmission line is received by coherent detection by an optical multicarrier signal receiver, demodulated by a digital signal processing device, and then a subcarrier signal constituting an optical multicarrier signal in a frame signal receiving device. By measuring the amount of bit delay between them and calculating the amount of chromatic dispersion using this amount of bit delay, the present invention can be applied to applications where it is essential to estimate the amount of chromatic dispersion with high accuracy.

  DESCRIPTION OF SYMBOLS 1 ... Optical signal receiver, 2 ... Optical signal transmitter, 3 ... Optical fiber transmission line, 10 ... Wavelength demultiplexer, 20 ... Optical multicarrier signal receiver, 30, 31 32, 33 ... digital signal processing device, 301, 310, 318 ... chromatic dispersion amount calculation circuit, 311, 312 ... chromatic dispersion compensation circuit, 313, 314 ... adaptive equalization circuit, 315, 316 ... carrier phase compensation circuit, 317, 318 ... demodulator circuit, 40, 41, 42 ... frame signal receiver, 420 ... chromatic dispersion calculation function, 50 ... client signal transmitter, 60 ... Client signal receiver, 70 ... Frame signal transmitter, 80, 90 ... Subcarrier transmitter, 100 ... Wavelength multiplexer

Claims (5)

An optical multicarrier signal receiver that demultiplexes an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) subcarrier signals and outputs a digital signal from the N subcarrier signals An optical signal receiving device comprising:
Digital signal processing means for inputting the digital signal, outputting a frame signal, and outputting a symbol rate of the subcarrier signal;
Client signal output means for inputting the output frame signal, processing the frame signal, and outputting a client signal;
Delay time output means for outputting a delay time generated between the subcarrier signals by dividing a bit delay amount between the frame signals by the symbol rate;
An optical signal receiving apparatus comprising: chromatic dispersion amount calculating means for calculating the chromatic dispersion amount of the optical fiber transmission line using the delay time. An optical multicarrier signal receiver that demultiplexes an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) subcarrier signals and outputs a digital signal from the N subcarrier signals An optical signal receiving device comprising:
Digital signal processing means for inputting the digital signal, outputting a frame signal, and outputting a symbol rate of the subcarrier signal and a center wavelength of the subcarrier signal;
Client signal output means for inputting the output frame signal, processing the frame signal, and outputting a client signal;
A delay amount output means for outputting a bit delay amount between the subcarrier signals from the frame signal;
A value obtained by dividing the bit delay amount between the frame signals by the symbol rate , and a value obtained by multiplying the value obtained based on the center wavelength by the chromatic dispersion amount of the optical fiber transmission line. An optical signal receiving device comprising: chromatic dispersion amount calculating means for calculating the chromatic dispersion amount so as to be equal . 3. The optical signal receiving apparatus according to claim 1, further comprising dispersion compensation means for compensating chromatic dispersion of the optical fiber transmission line based on the chromatic dispersion amount. An optical multicarrier signal receiver that demultiplexes an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) subcarrier signals and outputs a digital signal from the N subcarrier signals An optical signal receiving method performed by an optical signal receiving device comprising:
A digital signal processing step of inputting the digital signal, outputting a frame signal, and outputting a symbol rate of the subcarrier signal;
A client signal output step of inputting the output frame signal, processing the frame signal, and outputting a client signal;
A delay time output step of outputting a delay time generated between the subcarrier signals by dividing a bit delay amount between the frame signals by the symbol rate;
And a chromatic dispersion amount calculating step of calculating a chromatic dispersion amount of the optical fiber transmission line by using the delay time. An optical multicarrier signal receiver that demultiplexes an optical multicarrier signal input from an optical fiber transmission line into N (N is a natural number of 2 or more) subcarrier signals and outputs a digital signal from the N subcarrier signals An optical signal receiving method performed by an optical signal receiving device comprising:
A digital signal processing step for inputting the digital signal, outputting a frame signal, and outputting a symbol rate of the subcarrier signal and a center wavelength of the subcarrier signal;
A client signal output step of inputting the output frame signal, processing the frame signal, and outputting a client signal;
A delay amount output step of outputting a bit delay amount between subframe signals from the frame signal;
A value obtained by dividing the bit delay amount between the frame signals by the symbol rate , and a value obtained by multiplying the value obtained based on the center wavelength by the chromatic dispersion amount of the optical fiber transmission line. And a chromatic dispersion amount calculating step for calculating the chromatic dispersion amount so as to be equal to each other.

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