Bit-error probability for direct detection of optical RZ signal degraded by ASE noise and timing jitter

We analyze theoretically the interplay between optical return-to-zero signal degradation due to timing jitter and additive amplified-spontaneous-emission noise. The impact of these two factors on the performance of a square-law direct detection receiver is also investigated. We derive an analytical expression for the bit-error probability and quantitatively determine the conditions when the contributions of the effects of timing jitter and additive noise to the bit error rate can be treated separately. The analysis of patterning effects is also presented. © 2007 IEEE.

Patterning effects in a WDM RZ-DBPSK SMF/DCF optical transmission at 40 Gbit/s channel rate

Through extensive direct modelling we quantify the error statistics and patterning effects in a WDM RZ-DBPSK SMF/DCF fibre link using hybrid Raman/ EDFA amplification at 40 Gbit/s channel rate. We examine the BER improvement through skewed channel pre-coding reducing the frequency of appearance of the triplets 101 and 010 in a long data stream. © 2007 Elsevier B.V. All rights reserved.

Patterning effects in WDM RZ-DBPSK SMF/DCF optical transmission at 40 Gbit/s channel rate

Summary form only given. In this paper an important new example of a system with strong and nontrivial patterning effects is presented. There has been much interest lately in the implementation of the differential phase shift-keying (PSK) modulation format for long-haul and ultra long-haul fibre communications and, in particular, the differential binary PSK (DBPSK) modulation format, where data is encoded into the optical phase. The results of a direct computation of the error statistics for an SMF/DCF RZ-DBPSK 5-channel WDM RZ-DBPSK link with hybrid Raman/EDFA amplification at 40 Gbit/s per channel, with a channel separation of 100 GHz are presented. The statistics of bit triplets and quantify strong pattern-dependent ISI are obtained.

Optimal span length in high-speed transmission systems with hybrid Raman-erbium-doped fiber amplification

We show, using nonlinearity management, that the optimal performance in high-bit-rate dispersion-managed fiber systems with hybrid amplification is achieved for a specific amplifier spacing that is different from the asymptotically vanishing length corresponding to ideally distributed amplification [Opt. Lett. 15, 1064 (1990)]. In particular, we prove the existence of a nontrivial optimal span length for 40-Gbit/s wavelength-division transmission systems with Raman-erbium-doped fiber amplification. Optimal amplifier lengths are obtained for several dispersion maps based on commonly used transmission fibers. © 2005 Optical Society of America.

Non-Gaussian error probability in optical soliton transmission

We find the probability distribution of the fluctuating parameters of a soliton propagating through a medium with additive noise. Our method is a modification of the instanton formalism (method of optimal fluctuation) based on a saddle-point approximation in the path integral. We first solve consistently a fundamental problem of soliton propagation within the framework of noisy nonlinear Schrödinger equation. We then consider model modifications due to in-line (filtering, amplitude and phase modulation) control. It is examined how control elements change the error probability in optical soliton transmission. Even though a weak noise is considered, we are interested here in probabilities of error-causing large fluctuations which are beyond perturbation theory. We describe in detail a new phenomenon of soliton collapse that occurs under the combined action of noise, filtering and amplitude modulation. © 2004 Elsevier B.V. All rights reserved.

Nonlinearity management in fiber transmission systems with hybrid amplification

Nonlinearity management in transmission lines with periodic dispersion compensation and hybrid Raman-Erbium doped fiber amplification is studied both analytically and numerically. Different transmission/compensating fiber pairs are considered, with particular focus on the SMF/DCF case. © 2004 Elsevier B.V. All rights reserved.

Hybrid gain-flattened and reduced power excursion scheme for distributed Raman amplification

We propose and evaluate through extensive numerical modelling a novel distributed hybrid amplification scheme combining first and second-order Raman pumping which gives reduced signal power excursion over a wide spatial-spectral range of 60 km × 80 nm in C + L-bands. © 2013 Optical Society of America.

Pricing-to-market using EGARCH-error correction model

In this paper, the authors use an exponential generalized autoregressive conditional heteroscedastic (EGARCH) error-correction model (ECM), that is, EGARCH-ECM, to estimate the pass-through effects of foreign exchange (FX) rates and producers’ prices for 20 U.K. export sectors. The long-run adjustment of export prices to FX rates and producers’ prices is within the range of -1.02% (for the Textiles sector) and -17.22% (for the Meat sector). The contemporaneous pricing-to-market (PTM) coefficient is within the range of -72.84% (for the Fuels sector) and -8.05% (for the Textiles sector). Short-run FX rate pass-through is not complete even after several months. Rolling EGARCH-ECMs show that the short and long-run effects of FX rate and producers’ prices fluctuate substantially as are asymmetry and volatility estimates before equilibrium is achieved.

Multi-wavelength regeneration of differentially phase-encoded signals using phase sensitive amplification

We summarize the results of our recent demonstration of the first multi-channel regenerator for phase encoded signals. By developing a novel inline phase sensitive amplification scheme simultaneous suppression of deterministic phase distortion on two independent 42.66 Gbit/s DPSK modulated signal wavelengths was achieved. © 2012 SEE.

Nyquist-WDM PDM-QPSK transmission over SMF-28 fibre using URFL amplification

Nyquist-WDM PDM-QPSK transmission over standard SMF-28 fibre with novel distributed URFL amplification is reported for the first time. Transmission over 6157 km in a recirculating loop, and 320 km in an unrepeatered link without a ROPA were demonstrated. © 2014 IEEE.

Transmission comparison of ultra-long Raman fibre laser based amplification with first and dual order Raman amplification using 10×118 Gbit/s DP-QPSK

Experimental investigations of 10×118 Gbit/s DP-QPSK WDM transmission using three types of distributed Raman amplification techniques are presented. Novel ultra-long Raman fibre laser based amplification with second order counter-propagated pumping is compared with conventional first order and dual order counter-pumped Raman amplification. We demonstrate that URFL based amplification can extend the transmission reach up to a distance of 7520 km in comparison with 5010 km and 6180 km using first order and dual order Raman amplification respectively. © 2014 IEEE.

Dual-pump Raman amplification with enhanced flatness using modulation instability

In this work, we utilize modulation instability to the broadening of the two CW-pumps of a wideband Raman amplifier. Applying nonlinear fiber process, we demonstrate a feasibility of a certain control over the broadening process, leading to clear improvements in the flatness of the amplifier gain over its operational bandwidth.

Developments towards practical free-space quantum cryptography

We describe a free space quantum cryptography system which is designed to allow continuous unattended key exchanges for periods of several days, and over ranges of a few kilometres. The system uses a four-laser faint-pulse transmission system running at a pulse rate of 10MHz to generate the required four alternative polarization states. The receiver module similarly automatically selects a measurement basis and performs polarization measurements with four avalanche photodiodes. The controlling software can implement the full key exchange including sifting, error correction, and privacy amplification required to generate a secure key.

Nonlinearity management in hybrid amplification systems

A theory of nonlinearity management in transmission lines with periodic dispersion compensation and hybrid Raman-EDFA amplification is developed. Different transmission/compensating fiber pairs performances are compared and the optimal amplification scheme determined for each case.