Gilad Goldfarb

Electronic post-compensation of WDM transmission impairments using coherent detection and digital signal processing.

A universal post-compensation scheme for fiber impairments in wavelength-division multiplexing (WDM) systems is proposed based on coherent detection and digital signal processing (DSP). Transmission of 10 x 10 Gbit/s binary-phase-shift-keying (BPSK) signals at a channel spacing of 20 GHz over 800 km dispersion shifted fiber (DSF) has been demonstrated numerically.

Chromatic Dispersion Compensation Using Digital IIR Filtering With Coherent Detection

Digital infinite impulse response (IIR) filtering is proposed as a means for compensating chromatic dispersion in homodyne-detected optical transmission systems with subsequent digital signal processing. Compared to finite impulse response (FIR) filtering, IIR filtering achieves dispersion compensation (DC) using a significantly smaller number of taps. DC of 80 and 160 km in a 10-Gb/s binary phase-shift-keying is experimentally compared for the two filtering schemes. IIR filtering can achieve performance similar to the FIR filtering scheme.

BER estimation of QPSK homodyne detection with carrier phase estimation using digital signal processing

An approximate analytical expression for the bit error rate of a QPSK homodyne receiver employing digital signal processing for carrier recovery is derived. BER estimated using the analytical expression is in excellent agreement with Monte-Carlo simulations. The analytical approximation leads to an intuitive understanding of the trade off in such systems and allows optimization of system parameters without resorting to Monte-Carlo simulations.

Orthogonal Wavelength-Division Multiplexing Using Coherent Detection

Optical wavelength-division multiplexing (WDM) with channel spacing equal to the symbol rate is demonstrated. Coherent detection with subsequent digital signal processing is used for demultiplexing and demodulation. Experimental results for a 6-Gbaud binary phase-shift keying WDM transmission with a 6-GHz channel spacing achieve a Q-factor penalty of 2.8 dB compared to a single-channel transmission.

10 Channel, 100Gbit/s per channel, dual polarization, coherent QPSK, monolithic InP receiver photonic integrated circuit

A 10 channel, dual polarization, monolithically integrated, coherent QPSK receiver on InP operating at 100Gbit/s per channel is demonstrated.

Experimental Demonstration of Fiber Impairment Compensation Using the Split-Step Finite-Impulse-Response Filtering Method

Digital distributed impairment postcompensation for dispersion and nonlinear effects using backward propagation is demonstrated in a wavelength-division-multiplexing environment for the first time. The experimental results clearly show the benefit of employing distributed postcompensation, compared to dispersion compensation only or lumped dispersion and nonlinearity compensation.

Efficient backward-propagation using wavelet-based filtering for fiber backward-propagation

With the goal of reducing the number of operations required for digital backward-propagation used for fiber impairment compensation, wavelet-based filtering is presented. The wavelet-based design relies on signal decomposition using time-limited basis functions and hence is more compatible with the dispersion operator, which is also time-limited. This is in comparison with inverse-Fourier filter design which by definition is not time-limited due to the use of harmonic basis functions for signal decomposition. Artificial, after-the-fact windowing may be employed in this case; however only a limited amount of saving in the number of operations can be achieved, compared to the wavelets-base filter design. Wavelet-based filter design procedure and numerical simulations which validate this approach are presented in this paper.

10 channel, 45.6Gb/s per channel, polarization multiplexed DQPSK InP receiver photonic integrated circuit

We demonstrate a 10 wavelength, monolithically integrated, polarization multiplexed, InP DQPSK receiver operating at 45.6 Gbit/s per wavelength.

WDM Transmission over 320 km EDFA-Amplified SSMF Using 30 Gb/s Return-to-Zero Optical Differential 8-Level Phase-Shift Keying (OD8PSK)

Fiber transmission of optical differential 8-level phase-shift keying (OD8PSK) signals is demonstrated for the first time. Co-polarized 8 WDM channels of 10 Giga-symbol/s or 30 Gb/s return-to-zero (RZ) OD8PSK signals with a channel spacing of 50 GHz were transmitted over 320 km of standard single mode fiber (SSMF) with an EDFA spacing of 80 km. The BER of the worst WDM channel after transmission of 320 km was 2.3x10-5.

Experimental demonstration of fiber impairment compensation using the split-step infinite impulse response method

The use of infinite impulse response filtering for back-propagation of an optical signal is investigated. Experimental results and a comparison between several compensation techniques show the feasibility of this approach.