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Optical interconnects made of silicon are viewed as emerging efficient solutions for addressing the communication bottlenecks that plague high-performance computing systems and big-data centers. Due to large index contrast and optical nonlinearity of silicon, waveguides and active devices based on silicon can be scaled down to sub-wavelength size, making silicon photonics an ideal platform towards integrated on-chip photonic circuits. In order for this potential to be fulfilled, one needs to understand the factors that affect the quality of optical signals propagating in silicon optical interconnects, namely the bit-error ratio (BER), as well as the relationship between the parameters characterizing the optical signal and the BER.
In this work, an accurate approach to calculate the BER in single-channel silicon optical interconnects utilizing arbitrarily-shaped pulsed signals is presented. The optical interconnects consist of either strip single-mode silicon photonic waveguides (Si-PhWs) or silicon photonic crystal (PhC) waveguides (Si-PhCWs), and are linked to a direct-detection receiver. The optical signal consists of a superposition of Gaussian pulses and white noise. The signal dynamics in the silicon waveguides is modelled using a modified nonlinear Schrodinger equation, whereas the Karhunen-Loeve series expansion method is employed to calculate the system BER. Our analysis reveals that in the case of the Si-PhWs the pulse width is the main parameter that determines the BER, whereas in the case of Si-PhCWs the BER is mostly affected by the waveguide properties via the pulse group-velocity. A good system performance is achieved in centimeter-long Si-PhWs whereas similar system performance is obtained using 100× and 200× shorter Si-PhCWs operating in the fast- and slow-light regimes, respectively.
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