We propose a blind quadrature imbalance (QI) compensation algorithm based on the statistical properties of I and Q signals in a receiver. The algorithm estimates the QI parameters of a receiver by calculating the mean, variance, and correlation coefficient of I and Q components. Then, the estimated imbalance parameters are adopted to compensate for the QI in the receiver. Simulation results show that the Q factor is considerably optimized by the application of the QI compensation algorithm in an 80-Gb/s Pol-Mux coherent optical quadrature phase-shift keying (CO-QPSK) system. Compared with conventional algorithms, the proposed algorithm exhibits better performance when the phase deviation from QI exceeds +-15o.

The use of Bell Laboratories layered space-time (BLAST) architecture as a digital signal processing algorithm is proposed in this letter. It is aimed at improving the nonlinearity tolerance of a polarization division multiplexing (PDM) coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. The application of this channel estimation algorithm simulates system performance under different dispersion compensation (DC) maps. Simulation results show that, compared with intra-symbol frequency-domain averaging (ISFA) algorithm, at least 5-dB Q-factor improvement is achieved for the PDM CO-OFDM system at 112-Gb/s data rate over an 800-km standard single-mode fiber (SSMF) without DC.

A two-wavelength sinusoidal phase-modulating (SPM) laser diode (LD) interferometer for nanometer accuracy measurement is proposed. To eliminate the error caused by the intensity modulation, the SPM depth of the interference signal is chosen appropriately by varying the amplitude of the modulation current periodically. Then, the refine theory is induced to the measurement, and the two-wavelength interferometer (TWI) is combined with the single-wavelength LD interferometric technique to realize static displacement measurement with nanometer accuracy. Experimental results indicate that a static displacement measurement accuracy of 5 nm can be achieved over a range of 200 \mu m.

The microwave photonic filters (MPFs) based on serially coupled silicon microring resonators (MRRs) are theoretically analyzed for the application of 60-GHz millimeter wave wireless personal area networks. This is achieved by calculating the improvement of bit error ratio (BER). According to the simulation results, the requirement of signal-to-noise ratio (SNR) of the received data can be reduced by 14 dB for the same BER with and without MPFs. The performance of the MPF with five serially coupled microring structures is better than that of the MPF with a single microring, owing to the improvement of the shape factor.

Optical fiber interferometric sensors based on [3×3] couplers have been used in many fields. A new technique is proposed to demodulate output signals of this kind of sensors. The technique recovers the signal of interest by fitting coefficients of elliptic (Lissajous) curves between each fiber pair. Different from other approaches, this technique eliminates the dependence on the idealization of [3×3] coupler, provides enhanced tolerance to the variance of photoelectric converters, and is anti-polarization in a certain extent. The main algorithm has been successfully demonstrated both by numerical simulation and experimental result.

A fast automatic algorithm is proposed for baseline correction of infrared (IR) spectral signals. It is devised based on iterative curve fitting where orthogonal polynomials are used. The algorithm can process both emission and absorption spectra automatically without human intervention. Orthogonal polynomials are used for curve fitting to reduce computation time. Both emission and absorption spectra are obtained and the results demonstrate the feasibility and practicability of this algorithm.