Optical receiver having transient compensation
View Patent ↗An optical receiver having compensation for signal level transients. The receiver includes an OE converter, a transient threshold compensator, a threshold combiner and a CDR system. The OE converter receives the incoming optical signal and provides a modulated electrical signal having a high speed response for tracking the modulation on the optical signal and an averaged electrical signal having a moderate speed response for tracking changes in the average level of the optical signal. The transient threshold compensator processes the averaged electrical signal for providing a transient feedforward adjustment. The threshold combiner combines the transient feedforward adjustment with a lower speed BER feedback threshold adjustment for providing a decision threshold signal. The CDR system uses the decision threshold signal for recovering a clock, providing the BER feedback threshold adjustment, and estimating the data carried by the modulation.
1. An optical receiver, comprising:
an optical to electrical converter configured to convert an incoming optical signal having optical modulation to a modulated electrical signal having electrical modulation responsive to said optical modulation and an averaged electrical signal having an electrical level responsive to an average level of said optical signal;
a transient threshold compensator configured to receive said averaged electrical signal and issue a transient feedforward adjustment; and
a clock data recovery system including a clock recovery circuit configured to use a decision threshold signal based on said transient feedforward adjustment to recover a clock from said modulated electrical signal; and a data estimator configured to use said clock and said decision threshold signal to estimate data from said modulated electrical signal.
2. The receiver of claim 1 , further comprising:
a BER-based threshold controller configured to use a representation of bit error rate of said modulated electrical signal to provide a BER feedback threshold adjustment; and
a threshold combiner to combine said BER feedback threshold adjustment and said transient feedforward adjustment for providing said decision threshold signal.
3. The receiver of claim 2 , wherein:
said transient feedforward adjustment has a response time faster than said BER feedback threshold adjustment.
4. A method for receiving an optical signal, comprising:
converting an incoming optical signal having optical modulation to a modulated electrical signal having electrical modulation responsive to said optical modulation and an averaged electrical signal having an electrical level responsive to an average level of said optical signal;
generating a transient feedforward adjustment based upon said averaged electrical signal;
using a decision threshold signal based on said transient feedforward adjustment for recovering a clock from said modulated electrical signal; and
estimating data from said modulated electrical signal using said clock and said decision threshold signal.
5. The method of claim 4 , further comprising:
generating a BER feedback threshold adjustment based on a representation of bit error rate of said modulated electrical signal for providing a BER feedback threshold adjustment; and
combining said BER feedback threshold adjustment and said transient feedforward adjustment for providing said decision threshold signal.
6. The method of claim 5 , wherein:
said transient feedforward adjustment has a response time faster than said BER feedback threshold adjustment.
7. The receiver of claim 3 , wherein:
said response time for said transient feedforward adjustment is at least ten times faster than said BER feedback threshold adjustment.
8. The method of claim 6 , wherein:
said response time for said transient feedforward adjustment is at least ten times faster than said BER feedback threshold adjustment.