OSNR margin monitoring for optical coherent signals
A method and a device are provided for monitoring OSNR system margin in optical networks which relies on the relationship that exists between the OSNR value and the ESNR value.
1. A method for determining an optical signal-to-noise ratio (OSNR) system margin in an optical network, comprising:
receiving a coherent optical signal;
determining an OSNR and an electrical signal-to-noise ratio (ESNR) associated with the received coherent optical signal;
determining a reference ESNR for the received coherent optical signal;
determining a first parameter based on a transmission characteristic of the received coherent optical signal and a second parameter based on a physical impairment for an optical channel from which the coherent optical signal was received;
determining the OSNR system margin based on the first parameter and second parameter; and
monitoring changes over time in the OSNR system margin.
2. The method of claim 1 , further comprising determining an ESNR margin by comparing the determined ESNR with the reference ESNR.
3. The method of claim 2 , wherein the OSNR system margin is determined based on the ESNR margin.
4. The method of claim 1 , wherein the first parameter is retrieved from a database.
5. The method of claim 4 , wherein the database comprises an entry of the first parameter depending upon at least one of: a modulation format of the received coherent optical signal, a symbol rate of the received coherent optical signal, and an optical filtering mode.
6. The method of claim 1 , wherein the reference ESNR is retrieved from a database.
7. The method of claim 6 , wherein the database comprises an entry of the reference ESNR depending upon at least one of: a pre-defined bit error rate (BER) target, a symbol rate of the received coherent optical signal, a modulation format of the received coherent optical signal, and an optical filtering mode.
8. The method of claim 1 , wherein the reference ESNR is determined by increasing noise in the received coherent optical signal until a pre-defined BER is reached.
9. The method of claim 1 , wherein the second parameter is determined based on the first parameter.
10. The method of claim 1 , further comprising switching to another optical channel when the OSNR system margin is below a pre-defined threshold.
11. An apparatus for determining an OSNR system margin in an optical network, comprising:
a receiver configured to receive a coherent optical signal in a digitalized form;
at least one monitor configured to determine an OSNR and an ESNR associated with the received coherent optical signal; and
at least one processor configured to:
determine a reference ESNR;
determine a first parameter based on a transmission characteristic of the received coherent optical signal and a second parameter based on a physical impairment of a channel from which the coherent optical signal was received; and
determine the OSNR system margin based on the first parameter and second parameter; and
monitor changes over time in the OSNR system margin.
12. The apparatus of claim 11 , wherein the at least one processor is further configured to determine an ESNR margin by comparing the determined ESNR with the reference ESNR.
13. The apparatus of claim 12 , wherein the at least one processor is further configured to determine the OSNR system margin based on the ESNR margin.
14. The apparatus of claim 11 , wherein the first parameter is retrieved from a database.
15. The apparatus of claim 14 , wherein the database comprises an entry of the first parameter depending upon at least one of: a modulation format of the received coherent optical signal, a symbol rate of the received coherent optical signal, and an optical filtering mode.
16. The apparatus of claim 11 , wherein the reference ESNR is retrieved from a database.
17. The apparatus of claim 16 , wherein the database comprises an entry of the reference ESNR depending upon at least one of: a pre-defined BER target, a symbol rate of the received coherent optical signal, a modulation format of the received coherent optical signal, and an optical filtering mode.
18. The apparatus of claim 11 , further comprising a digital noise generator configured to generate a digital noise and wherein the at least one processor is further configured to determine the reference ESNR by combining the generated digital noise with the received coherent optical signal until a pre-defined BER target is reached.
19. The apparatus of claim 11 , wherein the at least one processor is further configured to determine the second parameter based on the first parameter.
20. The apparatus of claim 11 , wherein the at least one processor is further configured to switch to another optical channel when the OSNR system margin is below a pre-defined threshold.