Simple pre-distortion schemes for improving the power efficiency of SOA-based IR-UWB over fiber systems

Abstract

International audienceIn this paper, we investigate the usage of SOA for reach extension of an impulse radio over fiber system. Operating in the saturated regime translates into strong nonlinearities and spectral distortions, which drops the power efficiency of the propagated pulses. After studying the SOA response versus operating conditions, we have enhanced the system performance by applying simple analog pre-distortion schemes for various derivatives of the Gaussian pulse and their combination. A novel pulse shape has also been designed by linearly combining three basic Gaussian pulses, offering a very good spectral efficiency (>55%) for a high power (0 dBm) at the amplifier input. Furthermore, the potential of our technique has been examined considering a 1.5 Gbps-OOK and 0.75 Gbps-PPM modulation schemes. Pre-distortion proved an advantage for a large extension of optical link (150 Km), with an inline amplification via SOA at 40 Km

On phaser-based processing of impulse radio UWB over fiber systems employing SOA

“…Hence, the average signal power has to be reduced so as to meet the regular limit, leading to a significant impact on the power efficiency (degradation > 35%) at both operating points, specially for the noisy case. In our recent work [19], we have studied the power efficiency versus SOA input power while considering several peak-topeak voltages. It has been shown that high input powers bring strong nonlinearities specially at large V pp , and low powers are associated with a small signal-to-noise (SNR) ratio particularly at low V pp .…”

“…Table II states the parameters of applied waveforms, besides to the power efficiencies and spectral characteristics evaluated at SOA output. BL 34 is defined as the left -34 dB bandwidth (distance between the lower frequency f L and f peak ), this criterion is useful to evaluate the spectrum in correspondence with GPS band [19]. As shown, the same waveforms are generated in electrical domain, and chirping has no drawback on the pulse spectral behavior.…”

“…In our study, we investigate the usage of Semiconductor Optical Amplifier (SOA) [16] to perform this function, as it is a low cost optical component which is pertinent to be employed with simple impulse radio schemes. However, such a technique may lead to some drawbacks, mainly the Amplified Spontaneous Emission (ASE) noise produced [17], [18] and the nonlinear effects acting on the pulse waveform [19]. Both degrade the performance of the optical system, lower power efficiencies being achieved due to distortion, besides to the increased number of errors obtained at receiver side.…”

“…Various methodologies concerning these two topics have been investigated in literature [20]- [28]. The objective in [19] was to pre-distort against SOA nonlinear impairments by adjusting the parameters of input waveforms. This scheme was based on global optimization requiring a feedback in the electro-optical system.…”

Chirping techniques for enhancing the performance of SOA-based UWB over fiber systems: An experimental demonstration

“…A particular scenario of UWB is the Impulse Radio, which is a cost effective approach offering a low order of generation complexity [5] together with a simple design at the receiver side if a non-coherent detection is adopted [6]. With the view to get a reach extension in the optical access network, a low cost Semiconductor Optical Amplifier (SOA) has been recently employed [7,8]. However, a performance degradation may occur due to the nonlinear effects and Amplified Spontaneous Emission (ASE) noise inherent to SOA.…”