Performance monitoring device, method for performance monitoring of an optical system, and optical signal network

1. A performance monitoring device, PMD ( 100 ), for performance monitoring of an optical signal ( 71 ) having a first bandwidth,

the performance monitoring device ( 100 ) comprising a coherent receiver ( 10 ), an analog-to-digital-converter, ADC ( 20 ), a digital signal processing module, DSPM ( 30 ), and a noise correction module, NCM ( 40 ),

the receiver ( 10 ) having a second bandwidth that is smaller than the first bandwidth (BW 1 ) such that the receiver ( 10 ) is configured to output an electrical analog signal ( 72 ) with the second bandwidth based on the received optical signal ( 71 ) having the first bandwidth, the analog-to-digital converter, ADC ( 20 ), being configured to generate from the electric analog signal ( 72 ) a digital input signal ( 73 ) with the second bandwidth;

the digital signal processing module, DSPM ( 30 ), being configured to generate a raw performance monitoring metric, RPMM ( 74 ), based on the digital input signal ( 73 );

wherein the noise correction module, NCM ( 40 ), is configured to generate a performance monitoring metric, PMM ( 75 ), based on the digital input signal ( 73 ) by compensating distortion in the raw performance monitoring metric, RPMM ( 74 ), the distortion being caused by the coherent receiver ( 10 ) having a smaller bandwidth than the optical signal ( 71 ); and

wherein the second bandwidth is between about 5% and about 20% of the first bandwidth.

2. The device ( 100 ) of claim 1 ,

wherein the second bandwidth is between about 7.5% and about 17.5% of the first bandwidth.

3. The device ( 100 ) of claim 1 ,

wherein the first bandwidth (BW 1 ) is larger than about 50 GHz and/or wherein the second bandwidth is smaller than about 30 GHz.

4. The device ( 100 ) of claim 1 ,

wherein the receiver ( 10 ) is configured to receive a portion having the second bandwidth of the optical signal ( 71 ) that comprises a center frequency Ac of the optical signal ( 71 ).

5. The device ( 100 ) of claim 1 ,

wherein the performance monitoring metric, PMM ( 75 ), comprises a factor, in numerator or denominator, that is a sum of squared absolute values of time-domain Fourier coefficients h(i) of the digital input signal ( 73 ), for i=0 . . . . N, N being a predefined integer.

6. The device ( 100 ) of claim 5 ,

wherein the performance monitoring metric, PMM ( 75 ), comprises a factor, in numerator or denominator, that is a difference between:

a) the raw performance monitoring metric, RPMM ( 74 ), multiplied with the squared absolute value of the lowest-order time-domain Fourier coefficient h(0) and

b) the sum of squared absolute values of the remaining time-domain Fourier coefficient h(i) for i=1 . . . . N.

7. The device ( 100 ) of claim 1 ,

wherein the digital signal processing module, DSPM ( 30 ), is configured to generate the raw performance monitoring metric, RPMM ( 74 ), based on the digital input signal ( 73 ) by applying at least chromatic dispersion compensation to the digital input signal ( 73 ).

8. The device of claim 1 , configured to receive an optical signal with the first bandwidth comprising pilot symbols fulfilling any arbitrary autocorrelation function.

9. An optical signal network ( 1000 ), comprising at least one network node ( 200 , 300 ) and a performance monitoring device, PMD ( 100 ), according to claim 1 connected to the at least one network node ( 200 , 300 ), the performance monitoring device, PMD ( 100 ), configured to receive an optical signal ( 71 ) branched off at the at least one network note ( 200 , 300 ) and to generate the performance monitoring metric, PMM ( 75 ), for said optical signal ( 71 ).

10. The optical signal network ( 1000 ) of claim 9 ,

wherein the at least one network node is a multiplexer ( 200 ) and/or an amplifier ( 300 ).

11. The optical signal network ( 1000 ) of claim 9 ,

wherein the optical signal network ( 1000 ) comprises a computing device ( 500 ) and at least two performance monitoring devices, PMD ( 100 ), the computing device ( 500 ) being configured to receive performance monitoring metrics, PMM ( 75 ), from each of the at least two performance monitoring devices, PMD ( 100 ), and to determine a signal line quality metric, SLQM ( 76 ), based thereon.

12. A method for performance monitoring of an optical signal ( 71 ) having a first bandwidth, comprising at least steps of:

receiving (S 10 ) the optical signal ( 71 ) having the first bandwidth (BW 1 ) at a coherent receiver ( 10 ) having a second bandwidth that is smaller than the first bandwidth (BW 1 );

outputting (S 20 ), by the receiver ( 10 ), an electrical analog signal ( 72 ) with the second bandwidth based on the received optical signal ( 71 ) having the first bandwidth (BW 1 );

converting (S 30 ) the electrical analog signal ( 72 ) to a digital input signal ( 73 );

generating (S 50 ) a raw performance monitoring metric, RPMM ( 74 ), based on the digital input signal ( 73 );

generating (S 60 ) a performance monitoring metric, PMM, based on the digital input signal ( 73 ) by compensating distortion in the raw performance monitoring metric, RPMM ( 74 ), caused by the coherent receiver ( 10 ) having a smaller bandwidth than the optical signal ( 71 ); and

wherein the second bandwidth is between about 5% and about 20% of the first bandwidth.

13. The method of claim 12 ,

wherein the second bandwidth is between about 7.5% and about 17.5% of the first bandwidth.

14. The method of claim 12 ,

wherein the first bandwidth is larger than 50 GHz and/or wherein the second bandwidth is smaller than 20 GHz.

15. The method of claim 12 ,

wherein the performance monitoring metric, PMM ( 75 ), comprises a factor, in numerator or denominator, that is a sum of squared absolute values of time-domain Fourier coefficients h(i) of the digital input signal ( 73 ), for i=0 . . . . N, N being a predefined integer.