Analysis of intensity interference caused by cross-phase modulationin dispersive optical fibers

Under a set of broadly justified simplifying assumptions, an analytical approach to the problem of cross phase modulation in optical fibers is presented. Simple analytical expressions describing intensity interference caused by cross-phase modulation (XPM) are derived. It turns out that within a physically realizable range of parameters the power penalties induced by XPM have a linear dependence on the power of the interfering signal. Examples of specific systems are presented and discussed     

System impact of intra-channel nonlinear effects in highlydispersed optical pulse transmission

We provide accurate analytical estimates of timing- and amplitude-jitter caused by nonlinear pulse interaction in systems based on highly dispersed optical pulses, both for coherent and noncoherent pulse streams. We show that the system penalties reduce monotonically with pulsewidth and with increasing fiber dispersion. We demonstrate that proper dispersion pre-compensation can result in a significant reduction of the nonlinear inpairments and provide analytical tools for obtaining the optimal pre-compensation parameters     

Mean-square magnitude of all orders of polarization mode dispersionand the relation with the bandwidth of the principal states

Using the retarded plate model, we derive the correlations and the mean-square values of all orders of polarization mode dispersion (PMD) as well as the autocorrelation function of the PMD vector. Our results provide the signal bandwidth below which the first-order approximation of the principal states of polarization is valid. We show that this bandwidth depends only on the mean value of the differential group delay. Our theoretical results are supported by simulations and experiments     

The Brownian-bridge method for simulating polarization mode dispersion in optical communications systems

We propose a technique that allows efficient simulation of fibers with a specific value of instantaneous polarization mode dispersion (PMD) at a given optical frequency. The proposed technique is rigorously indistinguishable in the statistical sense from applying the brute-force Monte Carlo method and then selecting the fibers whose PMD vector has the desired value. To demonstrate the capabilities of the proposed method, we calculate the probability density function of the differential group delay (DGD) conditioned on the value of the DGD at an offset frequency.     

Signal-to-noise-ratio degradation caused by polarization-dependent loss and the effect of dynamic gain equalization

This paper describes a study of the effect of polarization-dependent loss (PDL) on the signal-to-noise ratio (SNR) in optical communications systems, taking into account the effect of dynamic gain equalization. The paper shows that the PDL-induced SNR penalty is caused by two distinct mechanisms related to the two polarization components of the amplified spontaneous emission noise generated in each amplifier. The noise components whose polarization is parallel to the signal at the various amplifier locations dominate the PDL-induced penalty in the absence of gain equalization. In the presence of even a moderate number of gain equalizers, the orthogonal noise components dominate the SNR degradation. Expressions are obtained relating the outage probability to the necessary performance margin that needs to be allocated for PDL.     

The effect of the frequency dependence of PMD on the performance of optical communications systems

The authors study numerically the importance of the frequency dependence of the polarization-mode dispersion (PMD) vector to the operation of optical systems and evaluate the validity of the second-order PMD approximation. They show that there is no relevant range of parameters in which the second-order PMD approximation is useful and question the validity of considering discrete high-orders of PMD.     

Optical DPASK and DQPSK: a comparative analysis for linear and nonlinear transmission

The performance of two multilevel modulation formats, differential-phase-amplitude shift-keying (DPASK) and differential quadrature-phase-shift keying (DQPSK), is compared for linear and nonlinear channels. For DPASK, the optimal extinction ratio is derived for both linear and nonlinear transmission. It is shown that for single-channel transmission, DQPSK outperforms DPASK in linear channels, whereas DPASK achieves better performance when nonlinear impairments are present.     

Balanced Versus Single-Ended Detection of DPSK: Degraded Advantage Due to Fiber Nonlinearities

We study the effect of nonlinear transmission on the receiver sensitivity advantage of differential-phase-shift-keying systems using balanced detection. We show how the accumulation of nonlinear phase noise owing to the Gordon-Mollenauer effect reduces the advantage of balanced detection, until it is completely eliminated in highly nonlinear scenarios. The results of our analysis are consistent with existing experimental observations     

Optoelectronic mixing using a short cavity distributed Braggreflector laser

We describe optoelectronic mixing in a short cavity distributed Bragg reflector laser operating near 1550 nm. Up and down conversion are demonstrated both theoretically and experimentally for three drive configurations. Absolute efficiencies as well as their frequency dependencies are described and the advantage of direct modulation of the photon field (by loss modulation) is clearly seen. Down conversion is shown to be less efficient than up conversion but its efficiency decrease with an increasing frequency is slower