Wideband SiN pulse interleaver for optically-enabled analog-to-digital conversion: a device-to-system analysis with cyclic equalization.

We present the design and experimental characterization of a silicon nitride pulse interleaver based on coupled resonator optical waveguide filters. In order to achieve a targeted free spectral range of 1.44 THz, which is large given the reduced optical confinement of the silicon nitride platform, individual ring resonators are designed with tapered waveguides. Its application to time-interleaved photonically-assisted ADCs is analyzed by combining experimental characterization of the photonic integrated circuit with a comprehensive model of the entire ADC. The impact of fundamental signal distortion and noise sources affecting the converter is investigated and suitable equalization techniques at the digital signal processing level are evaluated. The novel application of a simple but powerful equalization filter in the DSP domain allows for a significant improvement of the digitized signal SNR. An ENOB of 5 over a 75 GHz bandwidth (150 GS/s) and an ENOB of 4.3 over a 100 GHz bandwidth (200 GS/s) are expected to be achievable with compact and off-the-shelf single-section semiconductor mode locked lasers, that can be further improved with lower noise light sources.

Optically clocked switched-emitter-follower THA in a photonic SiGe BiCMOS technology.

In this paper a novel opto-electronic Track-and-Hold Amplifier (OE-THA) is presented. The OE-THA can be used as a sampler in a photonic analog-to-digital-converter (ADC). It is fabricated in a silicon photonic 250 nm SiGe BiCMOS technology to allow for monolithic integration of photonic and electronic components. The OE-THA chip exhibits a small signal bandwidth of over 65 GHz, a total harmonic distortion below -34 dB up to 75 GHz and a signal-to-noise and distortion ratio (SINAD) of over 35 dB (5.5 effective bits, ENOB) up to 45 GHz. The measured resolution bandwidth products result in a corresponding equivalent jitter of below 80 fs rms from 20 to 70 GHz. The best equivalent jitter is achieved at 41 GHz with a value of 55.8 fs rms. This is enabled by using a low-jitter optical pulse train, generated by a Mode-Locked-Laser (MLL), as an optical sampling clock. The circuit integrates all optical and electronic components besides the MLL. It draws 110 mA operated from a supply voltage of -4.6 V and occupies a silicon area of only 0.59 mm2.