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In this article we discuss a coherent optical heterodyne CPFSK receiver using optimum variable delay demodulation considering the effect of narrow-band IF filtering or intersymbol interference (ISI) caused by it. First we investigate the error probability an the normalized bandwidth of IF filter BT = 1 for a Gaussian IF filter. Numerical results show that the impact of narrow-band IF filtering increases with an increase in normalized IF spectral linewidth ΔνT and a decrease in modulation index h. Second, in order to decrease the impact off ISI, the optimum BT values are determined, which can minimize the error probability for given SNR. If a Gaussian IF filter is used, the optimal BT values are 1.3 for ΔνT = 0.25%, 1.4 for ΔνT = 0.5% at h = 0.5. 1.2 for ΔνT = 0.25%, 1.4 for ΔνT = 0.5% at h = 0.7. and 1.2 for all ΔνT ≤ 0.5% at h = 1. Finally, the performance of an optimal receiver employing optimum Gaussian IF filter is studied. We know that h = 1 is optimum and ΔνT ≤ 0.5% is necessary for 1-dB EB/N0 penalty per bit at BER of 10-9. [ABSTRACT FROM AUTHOR]

The system model for differential detection of optical heterodyne DPSK systems is set up, taking into account the effects of the IF filter and its production of ISI, the additive white Gaussian noise in the receiver and the quantum phase noise of lasers as well as the bandwidth-time product (BT). We derive the probability distribution function of noise statistics for BT ≥ I. The bit error rates (BER) are investigated in the presence of ISI, Numerical results for a 140-Mbit /s system are presented for Gaussian IF filters. It is found that the laser linewidth requirement is the same as the system that does not consider the IF filter effect and the ISI it causes. [ABSTRACT FROM AUTHOR]

Tunable terahertz beat signal generation is demonstrated by using a C-band InAs/InP quantum-dot (QD) mode-locked laser combined with external cavity of two fiber Bragg gratings (FBGs), where one of the FBGs is tunable in wavelength. Beat signals with ultra-high repetition rates quasi-continuously from 1 to 2.21 THz are observed between the two modes, which are phase-correlated due to intracavity four-wave mixing effect in the QD waveguide. [ABSTRACT FROM PUBLISHER]

We propose a novel and cost-effective frequency down-conversion technique for millimeter-wave (mm-wave)-over-fiber uplinks using an electroabsorption modulator (EAM) at the base station. It is found that the distributed optical local oscillator light from a central station can be directly modulated by the data signal down-converted from mm-wave inside the EAM and reused as the uplink optical signal with proper filtering. It is also demonstrated that the uplink mm-wave can be down-converted to either an intermediate frequency or the baseband. We numerically validate the feasibility of such a scheme and experimentally demonstrate the error-free performance by a total 40 km of fiber delivery with 1-dB receiver power penalty. [ABSTRACT FROM PUBLISHER]

We propose and investigate a linearized optical single-sideband (OSSB) Mach-Zehnder modulator (MZM) for radio-over-fiber systems. The linearized MZM makes use of a dual electrode z-cut LiNbO3 MZM with linear polarizers placed before and after it, respectively. By carefully selecting the angles of the two linear polarizers, third-order intermodulation and second-order distortion can be suppressed significantly. More importantly, it will be shown that with this linearized modulator, not only can OSSB modulation be obtained, but also an improvement in spurious free dynamic range of 15 dB is achieved as compared to the conventional MZM. [ABSTRACT FROM PUBLISHER]

We propose a new technique to reduce the bending- induced linear birefringence (LB) by fiber polarization rotator (FPR) in the reflective fiber-optical current sensor (FOCS). An accurate Jones matrix model was established. Such LB influence on FOCS performance is evaluated based on this model. A comparison was made between the proposed FPR scheme and the conventional scheme on measurement errors. Simulation shows that the proposed scheme has a large improvement on such LB reduction by an order of magnitude. [ABSTRACT FROM PUBLISHER]

We present a novel radio over fiber (RoF) balanced system that uses only one wavelength and one fiber. In this balanced system, the upper-side band (USB) and lower-side band (LSB) subcarriers, with an electrical phase difference of 180° between them, carry the same signal data. Thus, balanced detection of USB and LSB subcarriers with optical carriers will suppress even order nonlinear distortion. Simulation shows that the proposed balanced system outperforms previous balanced RoF systems in the reduction of second-order nonlinear distortion. [ABSTRACT FROM PUBLISHER]

Polarization-mode dispersion (PMD) penalty measurement on a 10-Gb/s deployment-ready dense wavelength-division-multiplexing (DWDM) long-haul transmission system is reported in this letter. We investigate the impact of self-phase modulation (SPM) and cross-phase modulation (XPM) on PMD penalty in the DWDM system. It is confirmed that SPM can suppress the PMD penalty, and XPM-induced polarization-scattering in DWDM systems can reduce the PMD impairment a little bit further. Our measurements suggest that it is necessary to carry out the PMD penalty test on DWDM systems rather than back-to-back systems in order to accurately allocate transmission margin of the systems. [ABSTRACT FROM PUBLISHER]

We demonstrate a simple black box model to evaluate both saturated gain and corresponding noise figure. This approach is simple and very suitable for system modeling with satisfied accuracy [ABSTRACT FROM PUBLISHER]

Substrate integrated waveguides (SIW) are built up of periodically arranged metallic via-holes or via-slots. The leakage loss of SIW structures increases with the distance between the viaholes or via-slots. An open periodic waveguide with a large via distance supports the propagation of leaky-wave modes and can thus be used for the design of a leaky-wave antenna. In this paper, this leakage loss is studied in detail and used to design a periodic leaky-wave antenna. The proposed concept represents an excellent choice for applications in the millimeter-wave band. Due to its versatility, the finite difference frequency domain method for periodic guided-wave or leaky-wave structures is used to analyze the characteristics of the proposed periodic leaky-wave antenna. Two modes (TE10 and TE20) are investigated and their different leaky-wave properties are analyzed. Based on the proposed leaky-mode analysis method, a novel periodic leaky-wave antenna at 28-34 GHz is designed and fabricated. [ABSTRACT FROM AUTHOR]

In this paper, we present a very compact ultra-wide-band (UWB) filter (patent pending), which is integrated in a commercial leaded package. This UWB filter is designed through quasi-equally allocating the first three resonant frequencies of the stub-loaded resonator. Input/output excitation is realized by a technique of wire-bonded interdigital capacitors for obtaining strong wideband coupling. After formulating the resonance conditions and analyzing the characteristics of the stub-loaded resonator, an equivalent-circuit topology is developed and a single-stage prototype is fabricated. Measured results agree well with the results generated from both circuit and full-wave simulations. In order to improve the selectivity, two stages of stub-loaded resonators are cascaded. A two-stage prototype is then assembled in a commercial leaded package and measured with a test fixture. Both simulation and measurement results validate our proposed design methods and packaging solutions. This filter is the first demonstration of integrated UWB filters with a commercial package, which can be conveniently applied in UWB communication and radar systems. [ABSTRACT FROM AUTHOR]