Recovering data from quadrature phase shift keying modulated optical signals
AssigneeZTE (USA) Inc.
InventorsJianjun Yu, Bo Huang
Life of this patent
Estimating the term…
Abstract
Systems, devices and techniques for processing received QPSK modulated optical signals include sampling the received signal at twice the baud rate, thereby producing samples that are then processed as 9-QAM symbols using a decision directed least squares optimization method. Data bits are then recovered from the resulting symbol estimates. The received optical signal may also include dual polarized signals for increased bandwidth capacity.
Claims15
A method of recovering data in an optical communication system, the method comprising:
- receiving an optical signal that is modulated using a quadrature phase shift keying (QPSK) modulation scheme;
- sampling the received optical signal to generate a group of samples comprising samples at time instances that are odd integer multiples of T/2, where T represents a symbol time interval of the QPSK modulation scheme;
- estimating received constellation symbols from the group of samples using a decision-directed least radius distance (DD-LRD) algorithm for blind equalization, wherein the DD-LRD algorithm includes iteratively refining symbol estimates using an adaptive filter;
- and
- recovering data bits transmitted in the optical signal from the estimated constellation symbols.
An optical communication receiver, comprising:
- an optical front end that receives a polarized modulation quadrature phase shift keying (PM-QPSK) signal;
- a timing synchronizer that produces a sampling signal indicative of sampling instances at odd multiples of half of a baud rate of the received PM-QPSK;
- a signal sampler that produces sample values of the received PM-QPSK at the sampling instances;
- a symbol generator that estimates received symbols from the sample values using a decision directed adaptive filtering method in which decisions about received symbols are iteratively improved using a feedback signal indicative of an error of calculation of previous decisions;
- a data recoverer that recovers data bits transmitted in the optical signal from the estimated received symbols.
A computer program product comprising a computer-readable medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a method of recovering data in an optical communication system, the method comprising:
- receiving an optical signal that is modulated using a quadrature phase shift keying (QPSK) modulation scheme;
- sampling the received optical signal to generate a group of samples comprising samples at time instances that are odd integer multiples of T/2, where T represents a symbol time interval of the QPSK modulation scheme;
- estimating received constellation symbols from the group of samples using a decision-directed least radius distance (DD-LRD) algorithm for blind equalization, wherein the DD-LRD algorithm includes iteratively refining symbol estimates using an adaptive filter;
- and
- recovering data bits transmitted in the optical signal from the constellation symbols.
Dependencies are inferred from the claim text.