Multi-wavelength pulse generation using flattop optical frequency comb and arrayed waveguide grating

A scheme of multi-wavelength pulse generator using optical frequency comb and arrayed waveguide grating (AWG) is proposed and experimentally demonstrated. A flattop optical frequency comb is shaped into multiple narrowband Gaussian spectra by using an AWG which contains a number of Gaussian channels, and then multi-wavelength optical pulses are achieved. In the experiment, six wavelength pulses with full width at half-maximum (FWHM) of 14.6 ps at 10 GHz are obtained, and two wavelength-interleaved pulse trains at 20 GHz and four wavelength-interleaved pulse trains at 40 GHz are demonstrated by using the multi-wavelength optical pulses. This scheme has flexibility because the pulse width, the repetition rate, and time-interval can be readily controlled.     

Flat-top optical frequency comb generation based on optical fiber-loop modulation with external injection

An optical frequency comb generation scheme using time-to-frequency conversion and optical fiber-loop modulation is proposed and demonstrated experimentally. Flat-top optical pulse train from an intensity modulator is injected into a fiber loop, which includes a phase modulator and an amplifier and is cyclically modulated by the phase modulator, to generate abundant optical comb lines. A total of 110 comb lines with 3-dB spectral power variation and 10-GHz frequency spacing are obtained. The proposed scheme is relatively simple and uses only one intensity modulator and one phase modulator.     

Experimental evaluation of resolution enhancement of a phase-shifted all optical analog-to-digital converter using an electrical analog-to-digital converter array

A resolution-improvement scheme of a phase-shifted analog-to-digital converter （ADC） is presented and experimentally demonstrated. To improve resolution via the scheme, the optical output of each quanti- zation channel is quantized by an electrical ADC with multiple thresholds instead of a comparator. A 9.9-GHz sinusoidal analog signal is sampled and quantized using the proposed enhancement scheme. The effective number of bits of 4.31 and the spur-free dynamic range of 40.89 dB are obtained, thus indicating an improvement of 0.66 bits and 7.47 dR. resnectivelv.