A.F. Elrefaie

Chromatic dispersion limitations in coherent lightwave transmission systems

Computer simulation is used to evaluate the chromatic dispersion limitations for both various coherent lightwave transmission systems and direct-detection on-off keying (OOK) systems. The results show that for a 2-dB dispersion penalty the maximum modulation rate ranges from 5 to 9 Gb/s for systems operating at 1.55 mu m with 15 ps/km-nm of chromatic dispersion and 100 km of fiber. The effect is less severe for OOK systems and most severe in coherent detection systems. Simulation results are in agreement with a available experimental data. >

Performance of directly modulated DFB lasers in 10-Gb/s ASK, FSK, and DPSK lightwave systems

A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber. >

Wide-linewidth phase diversity homodyne receivers

The use of phase diversity homodyne receivers, which have excellent performance even when the laser linewidth is of the same order of magnitude as the bit rate, to construct coherent systems with semiconductor lasers and moderate bandwidth receivers is considered. Theoretical, experimental, and computer simulation results of a study of a linewidth homodyne phase-diversity receiver is presented. A 150-Mb/s system with an IF linewidth of more than 50% of the bit rate is investigated in depth and is experimentally shown to operate within 1.8 dB from its theoretical limit. >

Effect of chirping-induced waveform distortion on the performance of direct detection receivers using traveling-wave semiconductor optical preamplifiers

The influence of chirping-induced waveform distortion on the performance of multigigabit-per-second traveling-wave semiconductor optical amplifier (TWSOA)/p-i-n direct detection receivers is evaluated. The results are based on a novel method of evaluating the probability of error in the presence of the signal-spontaneous and spontaneous-spontaneous beat noise components. Laser chirping causes the dependence of the receiver sensitivity on the fiber dispersion coefficient*length product DL to be different for TWSOA/p-i-n and avalanche photodiode (APD) receivers. Compared to the APD receiver, the sensitivity of the TWSOA/p-i-n receiver degrades less quickly. So for cases of practical interest, the TWSOA/p-i-n receiver is more tolerant of chirping-induced waveform distortion. >

A 2-Gbit/s optical FSK heterodyne transmission experiment using a 1520-nm DFB laser transmitter

Optical FSK transmission at 2 Gbit/s using a directly modulated DFB laser at 1520-nm wavelength is reported. A receiver sensitivity of \bar{P} = -36.7 dBm ( \eta\bar{P} = -39.2 dBm) at 10-9BER was achieved for transmission over 101 km of single-mode fiber with no additional penalty attributable to the fiber. The effect of the nonlinear phase of the transmitter FM response, and the system performance for discriminator demodulation, including the impact of laser phase noise, is analyzed and compared with experimental results.

A detailed comparison of the overall performance of 980 and 1480 nm pumped EDFA cascades in WDM multiple-access lightwave networks

A detailed comparison of the overall performance of 980 and 1480 mn pumped Er-doped fiber amplifier cascades over four different spectral regions of the usable amplifier band for multiple wavelength operation is presented. These comparisons are carried out by presenting a simple optimization method that relates the individual amplifier performance parameters to the overall performance of an amplifier cascade for best overall system performance. Issues considered are pump power, erbium-doped fiber length, accumulated ASE, inversion level, inter-amplifier fiber loss, and input signal levels and their spectral range.

Performance of directly modulated DFB lasers in multigigabit per second ASK, FSK, and DPSK lightwave systems

There is considerable interest in lightwave systems operating in the 10-20 Gbit/s range to meet future demand for higher transmission capacity. Direct modulation of the transmitter laser is attractive to avoid the insertion loss and additional systems complexity of external modulation.