This paper presents a robust video watermarking scheme in Discrete Fourier Transform (DFT) and Sequencyordered Complex Hadamard Transform (SCHT). The DFT and SCHT coefficients are complex and consist of both magnitude and phase and are well suited to adopt phase shift keying techniques to embed the watermark. In the proposed schemes, the phases of DFT and SCHT coefficients are modified to conve...

The rapid development of fiber-optic communication system requires a increasing transmission data rate and reach. One of the challenge for long-haul high-speed fiber-optic system is how to reduce the impairments and degrading effects from fiber dispersions and nonlinearity. Although the advances of digital signal processor (DSP) make impairment compensation for the coherent systems become possi...

We demonstrate a flexible-bandwidth network testbed with a real-time, adaptive control plane that adjusts modulation format and spectrum-positioning to maintain quality of service (QoS) and high spectral efficiency. Here, low-speed supervisory channels and field-programmable gate arrays (FPGAs) enabled real-time impairment detection of high-speed flexible bandwidth channels (flexpaths). Using p...

In this paper, we propose to extend the Guassian approximation (GA) method for reliable system performance evaluation from the traditional optical on-off keying (OOK) systems to the emerging optical differential phase shift keying (DPSK) systems. The proposed method can be used to guide efficient numerical estimate as well as experimental measurement of the noise-loading back-to-back DPSK syste...

We report on all-optical wavelength conversion of a 56 Gb/s differential quadrature phase shift keying signal and a 42.7 Gb/s on-off keying signal. Wavelength conversion is based on four-wave mixing effect in a 1 m long highly nonlinear GeAsSe chalcogenide fiber. The high nonlinearity of the fiber allows low-power penalty operation with a total average power of less than 60 mW.

Differential-quadrature phase-shift-keying (DQPSK) can, unlike on-off-keying (OOK), be impaired by nonlinear phase noise (NPN). It has been shown that optical phase conjugation (OPC) is an effective compensation scheme for NPN resulting from the ASE of EDFAs (ASE-NPN). In this paper we discuss the influence of NPN resulting from modulator imperfections (MI-NPN). We show that MI-NPN can be compe...

We summarize three electrical decision schemes that have been proposed for 8-level differential phase-shift keying, briefly discuss their performance and complexity, and comment that two of these schemes have been confused in an earlier comparison in Optics Express.

In this paper, the design of a wideband RF signal generator for demodulator/receiver testing is presented. The design of test generator is based on direct digital synthesizer (DDS) and voltage-controlled oscillator (VCO), controlled by microprocessor. It provides generation of arbitrary waveform signal up to 4.5 GHz. Output signal level is adjustable with precision of 0.5 dB. Dynamic range of R...

All-optical regeneration of differential phase-shift keying signals based on phase-sensitive amplification is described. Nearly ideal phase regeneration can be achieved in the undepleted-pump regime, and simultaneous amplitude and phase regeneration can be realized in the depleted-pump regime.

Recently, optical differential phase shift keying (DPSK) has attracted much interest in high-speed optical transmission systems. It features constant intensity and thus is less vulnerable to the fiber nonlinearities. In addition to high-speed data transmission, it is desirable to carry relatively low-speed supervisory information simultaneously to facilitate the system monitoring and network ma...