Method and apparatus for estimating polarization dependent loss and receiving device

Patent metadata

Field	Value
Publication number	US-2018123700-A1
Application number	US-201715720620-A
Country	US
Kind code	A1
Filing date	Sep 29, 2017
Priority date	Oct 31, 2016
Publication date	May 3, 2018
Grant date	—

Abstract

Embodiments of this disclosure provide a method and apparatus for estimating polarization dependent loss (PDL) and a receiving device. The method includes: performing equalization processing on pre-processed dual-polarization state signals; performing correlation operations on the equalized dual-polarization state signals and unequalized dual-polarization state signals; constructing an estimation matrix based on a result of the correlation operations; and calculating a polarization dependent loss of the dual-polarization state signals by using one or more feature values of the estimation matrix. Hence, not only PDL in an optical fiber link may be accurately estimated, but also off-line digital signal processing may be performed at a receiver, without needing to incur extra hardware overhead.

First claim

1 . An apparatus for estimating polarization dependent loss, configured in a receiving device receiving dual-polarization state signals, the apparatus comprising:
an equalizer configured to perform equalization processing on pre-processed dual-polarization state signals; a correlator configured to perform correlation operations on the equalized dual-polarization state signals and unequalized dual-polarization state signals; a constructor configured to construct an estimation matrix based on a result of the correlation operations; and a calculator configured to calculate a polarization dependent loss of the dual-polarization state signals by using one or more feature values of the estimation matrix.

2 . The apparatus according to claim 1 , wherein the correlator is configured to:
perform inter-correlation operations on the equalized H-polarization state signals and unequalized H-polarization state signals; perform inter-correlation operations on the equalized H-polarization state signals and unequalized V-polarization state signals; perform inter-correlation operations on the equalized V-polarization state signals and unequalized H-polarization state signals; and perform inter-correlation operations on the equalized V-polarization state signals and unequalized V-polarization state signals.

3 . The apparatus according to claim 2 , wherein the correlator comprises:
a conjugator configured to, for each inter-correlation operation, conjugate a route of signals performing the inter-correlation operation; a delayer configured to perform delay on another route of signals performing the inter-correlation operation; a vector obtainer configured to multiply the delayed signals by the conjugated signals, and take an expected value of a result of multiplication, so as to obtain a correlation value vector; and a value taker configured to determine a position of a maximum modulus value in the correlation value vector, and obtain a correlation value to which the position of the maximum modulus value corresponds.

4 . The apparatus according to claim 2 , wherein the correlator comprises:
a conjugator configured to, for each inter-correlation operation, conjugate a route of signals performing the inter-correlation operation; and a correlation value obtainer configured to multiply two routes of signals performing the inter-correlation operation after aligning them, and take an expected value of a result of multiplication, so as to obtain a correlation value.

5 . The apparatus according to claim 1 , wherein the estimation matrix constructed by the constructor based on the result of the correlation operation is expressed as follows:

A
=

[

M
1

M
2

M
3

M
4

]

where, A is the estimation matrix;
M 1 is a correlation value to which a position of a maximum modulus value in a correlation value vector obtained after the inter-correlation operations are performed on the equalized H-polarization state signals and the unequalized H-polarization state signals corresponds, or is a correlation value obtained after the inter-correlation operations are performed on the equalized H-polarization state signals and the unequalized H-polarization state signals;
M 2 is a correlation value to which a position of a maximum modulus value in a correlation value vector obtained after the inter-correlation operations are performed on the equalized V-polarization state signals and the unequalized H-polarization state signals corresponds, or is a correlation value obtained after the inter-correlation operations are performed on the equalized V-polarization state signals and the unequalized H-polarization state signals;
M 3 is a correlation value to which a position of a maximum modulus value in a correlation value vector obtained after the inter-correlation operations are performed on the equalized H-polarization state signals and the unequalized V-polarization state signals corresponds, or is a correlation value obtained after the inter-correlation operations are performed on the equalized H-polarization state signals and the unequalized V-polarization state signals;
and M 4 is a correlation value to which a position of a maximum modulus value in a correlation value vector obtained after the inter-correlation operations are performed on the equalized V-polarization state signals and the unequalized V-polarization state signals corresponds, or is a correlation value obtained after the inter-correlation operations are performed on the equalized H-polarization state signals and the unequalized V-polarization state signals.

6 . The apparatus according to claim 1 , wherein the calculator comprises:
a singular value decomposer configured to perform singular value decomposition on the estimation matrix; a feature value obtainer configured to obtain the feature values based on the decomposed matrix; and a loss obtainer configured to calculate a value of the polarization dependent loss by using the feature values, and obtain rotational angles of the polarization dependent loss by using the decomposed matrix.

7 . The apparatus according to claim 6 , wherein the singular value decomposed estimation matrix is expressed as follows:
A=U×S×V T ; where, A is the estimation matrix, U is a 2×2 unitary matrix, S is a 2×2 diagonal matrix, and V is a 2×2 unitary matrix.

8 . The apparatus according to claim 7 , wherein the loss obtainer is further configured to: obtain the value of the polarization dependent loss based on a ratio of elements in a diagonal of the matrix S, and respectively obtain a first rotational angle and a second rotational angle of the polarization dependent loss based on the matrix V and the matrix U.

9 . A method for estimating polarization dependent loss, applicable to a receiving device receiving dual-polarization state signals, the method comprising:
performing equalization processing on pre-processed dual-polarization state signals; performing correlation operations on the equalized dual-polarization state signals and unequalized dual-polarization state signals; constructing an estimation matrix based on a result of the correlation operations; and calculating a polarization dependent loss of the dual-polarization state signals by using one or more feature values of the estimation matrix.

10 . A receiving device, comprising:
an optical-to-electrical converter configured to convert received dual-polarization state optical signals into electrical signals; and a digital signal processor configured to perform equalization processing on pre-processed dual-polarization state signals, perform correlation operations on the equalized dual-polarization state signals and unequalized dual-polarization state signals, construct an estimation matrix based on a result of the correlation operations, and calculate a polarization depend

Assignees

• Fujitsu Ltd

Inventors

• Li Huihui
• Zhao Ying
• Tao Zhenning

Classifications

• H04B10/6166

  Polarisation demultiplexing, tracking or alignment of orthogonal polarisation components · CPC title

• H04B10/6162 Primary

  Compensation of polarization related effects, e.g., PMD, PDL · CPC title

• H04B10/0795

  Performance monitoring; Measurement of transmission parameters · CPC title

• H04B10/2572 Primary

  due to forms of polarisation-dependent distortion other than PMD · CPC title

• H04L25/03184

  Details concerning the metric · CPC title