Calculating apparatus and method for nonlinear weighting coefficient

Patent metadata

Field	Value
Publication number	US-9998223-B2
Application number	US-201514879374-A
Country	US
Kind code	B2
Filing date	Oct 9, 2015
Priority date	Apr 10, 2013
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

Embodiments of the present disclosure provide a calculating apparatus and method for nonlinear weighting coefficient. The calculating apparatus for nonlinear weighting coefficient includes: an approximation processing unit configured to use a rational function to perform approximation processing on a link loss/gain function in intra-channel nonlinear distortion estimation; and a coefficient calculating unit configured to calculate a nonlinear weighting coefficient in the nonlinear distortion estimation by using the approximated link loss/gain function and a large dispersion approximation, to obtain an analytical closed solution of the nonlinear weighting coefficient. With the embodiments of the present disclosure, a weighting coefficient of high precision may be obtained, thereby performing high-precision estimation on nonlinear distortion in case of loss.

First claim

The invention claimed is:

1. A calculating apparatus for a nonlinear weighting coefficient, comprising:
a digital signal processor,
the digital signal processor is configured to:
divide an optical fiber of a transmission link into multiple optical fiber spans;
for each optical fiber span, use a rational function to perform approximation processing on a link loss/gain function in intra-channel nonlinear distortion estimation;
calculate one or more nonlinear weighting coefficients in the nonlinear distortion estimation by using an approximated link loss/gain function and a dispersion approximation; and
perform summation of nonlinear weighting coefficients of respective obtained different optical fiber spans, to obtain an analytical closed solution of the nonlinear weighting coefficient of the transmission link,
wherein the processor is further configured to use an equation to perform approximation processing on the link loss/gain function, the equation comprising:

G
⁡

(

z
i

)

=

exp
⁡

(

-
α

⁢

⁢

z
i

)

≈

(

N
/
α

)

N

(

z
i

+

N
/
α

)

N

=

(

N

α
⁢

⁢

z
i

+
N

)

N

;

wherein, G(z i ) is the link loss/gain function, N is an attenuation control factor, α is an attenuation coefficient of the optical fiber, and z i is a transmission distance in an i-th section of the optical fiber.

2. The calculating apparatus for the nonlinear weighting coefficient according to claim 1 , wherein the processor is further configured to:
use a dispersion distribution function to perform integral processing on the nonlinear weighting coefficient in the nonlinear distortion estimation; and
calculate an integral-processed nonlinear weighting coefficient by using the approximated link loss/gain function and the large dispersion approximation.

3. The calculating apparatus for the nonlinear weighting coefficient according to claim 1 , wherein the processor is further configured to use one of the functions as follows a Gaussian pulse function and a non-return-to-zero pulse function and a return-to-zero pulse function and a Nyquist pulse function, to approximate pulse shapes in the intra-channel nonlinear distortion estimation.

4. A pre-compensating apparatus for a nonlinear distortion, comprising:
a digital signal processor,
the digital signal processor is configured to:
divide an optical fiber of a transmission link into multiple optical fiber spans;
for each optical fiber span, use a rational function to perform approximation processing on a link loss/gain function in intra-channel nonlinear distortion estimation;
calculate one or more nonlinear weighting coefficients in the nonlinear distortion estimation by using an approximated link loss/gain function and a dispersion approximation;
perform summation of nonlinear weighting coefficients of respective obtained different optical fiber spans, to obtain an analytical closed solution of the nonlinear weighting coefficient of the transmission link;
use the nonlinear weighting coefficients to calculate vector perturbation items superimposed on a transmitted signal; and
use the vector perturbation items to pre-compensate the transmitted signal to obtain a pre-distorted signal inputted into a transmitter,
wherein the processor is further configured to use an equation to perform approximation processing on the link loss/gain function, the equation comprising:

G
⁡

(

z
i

)

=

exp
⁡

(

-
α

⁢

⁢

z
i

)

≈

(

N
/
α

)

N

(

z
i

+

N
/

Assignees

• Fujitsu Ltd

Inventors

• Zhao Ying
• Dou Liang
• Tao Zhenning

Classifications

• H04B10/61

  Coherent receivers · CPC title

• H04B10/58

  Compensation for non-linear transmitter output · CPC title

• H04B10/2543 Primary

  due to fibre non-linearities, e.g. Kerr effect · CPC title

• H04B10/6163

  Compensation of non-linear effects in the fiber optic link, e.g. self-phase modulation [SPM], cross-phase modulation [XPM], four wave mixing [FWM] · CPC title

• H04B10/60

  Receivers · CPC title