Spectrum-sliced WDM Systems Research Articles

Noise suppression of incoherent light using a gain-saturated SOA: implications for spectrum-sliced WDM systems

In this paper, we present an experimental and numerical study of semiconductor optical amplifier (SOA)-based noise suppression and its relevance to high-channel-density spectrum-sliced wavelength-division-multiplexed systems. We show that the improvement in signal quality is accompanied by spectral distortion, which renders it susceptible to deterioration in the presence of subsequent optical filtering. This phenomenon originates from the loss of intensity correlation between spectral components of the SOA output when the signal spectrum is altered. As a consequence, a design tradeoff is introduced between intensity noise and crosstalk in high-channel-density systems. These adverse effects can be overcome by optimized SOA design, resulting in a significant improvement in signal quality.

Analysis and optimization of intensity noise reduction in spectrum-sliced WDM systems using a saturated semiconductor optical amplifier

Theoretical and experimental results on the reduction of the intensity noise in spectrum-sliced wavelength-division-multiplexing systems using a saturated semiconductor optical amplifier (SOA) are presented. The influence of the injected current and the input power to the saturated SOA on the noise reduction and its bandwidth are studied. The optimum condition for a high noise suppression ratio and a large bandwidth is derived. For the optimum operation of the SOA, an increase of 13.5 dB in the intensity-noise-limited signal-to-noise ratio for a bitrate of 2.488 Gb/s and of 17.5 dB for a bitrate of 622 Mb/s are obtained experimentally in a single-stage SOA.

Reduction of excess intensity noise in spectrum-sliced incoherent light for WDM applications

We investigate wideband reduction of excess intensity noise in incoherent light for application to spectrum-sliced WDM systems. The noise reduction scheme is based on optoelectronic feedforward compensation. We derive expressions for the probability density function of noise-reduced incoherent light and present measurements that are in good agreement with theory. We evaluate the significant levels of improvement obtainable in the capacity of spectrum-sliced WDM channels. For example, to obtain a signal-to-noise ratio of 50, a noise-reduced channel requires six times less optical bandwidth than a spectral slice without noise reduction.

Transmission performance of high bit rate spectrum-sliced WDM systems

We simulate transmission of a spectrum-sliced WDM channel operating at high bit rates (e.g., 622 to 2488 Mb/s). We calculate the bit error rate using the non-Gaussian statistics of thermal light sources that are commonly used in spectrum slicing and account for the effects of fiber dispersion. We evaluate the tradeoff in optical slice linewidth between signal-to-excess optical noise ratio and dispersion penalty in spectrum-sliced WDM systems, and determine the channel slicewidth that minimizes transmission penalty for a given link length and bit rate. We compare our simulations against the measured performance of a 1244 Mb/s channel over 20 km of fiber. The results in this paper provide useful information for the design of spectrum-sliced WDM networks.

Influence of Receiver Threshold Setting and Source Extinction Ratio on the Performance of Spectrum Sliced WDM Systems

Receiver decision threshold setting is found to be critically important if the performance capabilities of spectrum sliced systems with narrow optical filters/channel spacing can be realized. We fined also that source extinction ratio is a severe source of degradation, markedly more so than for conventional systems.

Transmission of 622 Mbit/s spectrum-sliced WDM channelover 60 km of nondispersion-shifted fibre at 1550 nm

The transmission of a spectrum-sliced WDM channel at 622 Mbit/s over 60 km of nondispersion-shifted fibre using an optical bandwidth of only 0.23 nm is reported. This is the highest single channel bit rate-length product (40 Gbit/s·km) and smallest channel bandwidth reported to date for spectrum-sliced WDM systems. The bit error rate performance is theoretically predicted and experimentally confirmed and limits on the bit rate-length products of spectrum-sliced WDM channels using nondispersion-shifted fibre in the 1550 nm window are given.

100 mW spectrally-uniform broadband ASE source forspectrum-slicedWDM systems

A > 100mW source of broadband ASE with exceptionally flat spectral density and 22nm bandwidth is presented. The source is ideally suited for spectrum-sliced WDM systems. Data transmission at 622Mbit/s using a spectraily-sliced channel tuned over a 15nm range is demonstrated.