The reflective semiconductor optical amplifier (RSOA) capability to compress the relative intensity noise (RIN) is well-known and widely exploited in wavelength division multiplexing passive optical networks (WDM PON). While this feature has been previously analysed using SOA theory, in this paper we show that RSOAs present specific gain saturation properties. According to the injected power, three nonlinear operation regimes can be highlighted: the first one, where RIN is moderately compressed, the second one, where RIN maximum compression takes place, and the final one, where RIN grows again, this last regime being RSOA specific. We focus on a spectrum-sliced WDM PON classical topology, evaluating the impact of the injection process and filtering. RSOA injection and optical filtering have opposite effects on the RIN: by injection into the RSOA the RIN is reduced, after filtering RIN increases. We experimentally evaluate RIN both in the time and in the spectral domain. A simple numerical model mainly based on the correct reproduction of the component gain behaviour is exploited to verify experimental results. Through our experimental analysis and by simulations, we identify the correct injected power range to best take advantage of the RSOA features.

To face the increased demand for bandwidth, cost-effectiveness and simplicity of future Ethernet data communications, a comparison between two different solutions based on directly-modulated VCSEL sources and Silicon Photonics technologies is carried out. Also by exploiting 4-PAM modulation, the transmission of 50-Gb/s and beyond capacity per channel is analyzed by means of BER performance. Applications for optical backplane, very short reach and in case of client-optics networks and intra and inter massive data centers communications (up to 10 km) are taken into account. A comparative analysis based on the power consumption is also proposed.

1.55-microm single-mode VCSEL frequency chirp behavior is investigated in under-threshold and above-threshold operating conditions for different VCSEL-to-VCSEL injection locking configurations with respect to free-running case. We experimentally evaluated the capability of adjusting the frequency chirp, reducing its value and inverting the sign. The control over the frequency chirp is obtained changing the wavelength detuning and power injection ratio between the VCSEL master and the VCSEL slave. Advantages of the chirp inversion are demonstrated for 10 Gb/s error-free propagation at 1.55-microm over 40-km standard single mode fiber without any dispersion compensation.

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