Communication system employing self-tuning optical transceivers
An optical transceiver capable of optimizing the performance of the corresponding optical channel by dynamically adjusting the optical power of the output signal in response to the FEC-performance data received from the corresponding remote transceiver. In an example embodiment, the FEC-performance data can be exchanged by the two optical transceivers using a dedicated field in the overhead of the transmitted data frames. The power-adjustment process is configured to be relatively slow to prevent the occurrence of transients on other optical channels and ensure stable operation of the corresponding WDM system as a whole, while different transceivers thereof are allowed to adjust their respective output powers in an autonomous way and independent of each other. The performance optimization can be directed at meeting a predefined performance target specified by the system designer or operator while driving the operating point away from conditions under which nonlinear optical effects may become relatively prominent.
1. An apparatus comprising an optical data receiver, an optical data transmitter, and an electronic controller connected therebetween, the optical data receiver including a photodetector configured to detect an optical input signal carrying a first data frame, the optical data transmitter including a laser configured to generate a carrier wavelength for an optical output signal;
wherein the optical data receiver comprises a frame decoder configured to read a first value of a measure of transmission quality from the first data frame, the measure of transmission quality representing an error rate at which an FEC code used at a remote receiver encounters errors in data transmitted using the optical output signal; and
wherein the electronic controller is configured to:
determine a sign of a slope of the measure of transmission quality with respect to an optical output power of the laser; and
change the optical output power of the laser based on said sign and the first value of the measure of transmission quality provided thereto by the frame decoder.
2. The apparatus of claim 1 , wherein the measure of transmission quality is one of:
a quality factor Q 2 corresponding to the error rate;
a Q value derived from the quality factor Q 2 and expressed in decibel;
a number of errors per data frame corrected by the FEC code; and
an optical signal-to-noise ratio corresponding to the quality factor Q 2 .
3. The apparatus of claim 1 ,
wherein the frame decoder is further configured to count a number of errors corrected in the first data frame using an FEC data block thereof;
wherein the electronic controller is configured to compute a second value of the measure of transmission quality using the number of errors counted by the frame decoder;
wherein the optical data transmitter comprises a frame generator configured to write the second value of the measure of transmission quality into a second data frame; and
wherein the optical data transmitter is configured to cause the optical output signal to carry the second data frame.
4. The apparatus of claim 3 , wherein the frame generator is further configured to include an FEC data block into the second data frame, the FEC data block of the second data frame being computed using an overhead of the second data frame and a payload of the second data frame, the overhead being configured to carry one or more values of the measure of transmission quality.
5. The apparatus of claim 1 , further comprising a plurality of optical data transmitters, each configured to use a different respective carrier wavelength, the optical data transmitter being one of the plurality.
6. The apparatus of claim 1 , further comprising a plurality of optical data receivers, each configured to receive a different respective carrier wavelength, the optical data receiver being one of the plurality.
7. The apparatus of claim 1 , wherein the electronic controller is configured to change the optical output power of the laser to cause a value of the measure of transmission quality from another data frame received by the optical data receiver from the remote receiver at a later time to be within a predetermined fixed range of values.
8. The apparatus of claim 1 , wherein the electronic controller is configured to dynamically change the optical output power of the laser in response to a sequence of values of the measure of transmission quality, each of said values being read from a different respective data frame carried by the optical input signal.
9. The apparatus of claim 1 , wherein the first data frame comprises an optical transport unit generated in accordance with an ITU-T G.709/Y.1331 Recommendation.
10. The apparatus of claim 1 , wherein the electronic controller is configured to change the optical output power of the laser by an increment determined in response to the first value of the measure of transmission quality, the increment being smaller than or equal to a predetermined fixed value.
11. The apparatus of claim 1 , wherein the electronic controller is configured to store therein a history of power changes, each entry in the history including a respective optical output power of the laser and a corresponding value of the measure of transmission quality received from the remote receiver.
12. The apparatus of claim 1 , wherein the electronic controller is configured to decrease the optical output power of the laser if said sign is negative.
13. At an optical transceiver, a communication method comprising:
receiving an optical input signal carrying a first data frame;
decoding the first data frame to read a first value of a measure of transmission quality from the first data frame, the measure of transmission quality representing an error rate at which an FEC code used at a remote receiver encounters errors in data received from the optical transceiver;
determining a sign of a slope of the measure of transmission quality with respect to an optical output power of a laser; and
changing the optical output power of the laser based on said sign and the first value of the measure of transmission quality, the laser being configured to generate a carrier wavelength for an optical output signal directed to the remote receiver.
14. The communication method of claim 13 , further comprising:
counting a number of errors corrected in the first data frame using an FEC data block thereof;
computing a second value of the measure of transmission quality using the number of errors;
writing the second value of the measure of transmission quality into a second data frame; and
transmitting the optical output signal to the remote receiver, the optical output signal being configured to carry the second data frame.
15. The communication method of claim 14 , further comprising including an FEC data block into the second data frame, the FEC data block of the second data frame being computed using an overhead of the second data frame and a payload of the second data frame, the overhead being configured to carry one or more values of the measure of transmission quality.
16. The communication method of claim 13 , wherein the changing comprises decreasing the optical output power of the laser if said sign is negative.
17. An apparatus comprising an optical data receiver, an optical data transmitter, and an electronic controller connected therebetween, the optical data receiver including a photodetector configured to detect an optical input signal carrying a first data frame, the optical data transmitter including a laser configured to generate a carrier wavelength for an optical output signal;
wherein the optical data receiver comprises a frame decoder configured to read a first value of a measure of transmission quality from the first data frame, the measure of transmission quality representing an error rate at which an FEC code used at a remote receiver encounters errors in data transmitted using the optical output signal; and
wherein the electronic controller is configured to:
change an optical output power of the laser in response to the first value of the measure of transmission quality provided thereto by the frame decoder; and
store therein a history of power changes, each entry in the history including a respective optical output power of the laser and a corresponding value of the measure of transmission quality received from the remote receiver.