Time- and wavelength-interweaved photonic sampler for analog-to-digital conversion

Summary form only given. We present a hybrid optoelectronic analog-to-digital converter architecture with a photonic signal sampler based on the time interweaving of spectrally distinct pulses. Broadband mode-locked pulses (/spl tau//sub p//spl sim/1 ps, /spl Delta//spl lambda//spl sim/ 50 nm) from a stretched-pulse fiber ring laser (MLFL) were spectrally sliced by an eight channel wavelength division multiplexer (WDM) to form eight wavelength discrete channels. Connected to each channel was a fiber stretcher (FS), variable attenuator (AT), delay loop (DL) and Faraday mirror (FM). Dispersion shifted fiber was used to reduce the pulse broadening and the relative dispersion between each Channel. The Faraday mirror provided birefringence compensation as well as a second pass through the WDM with the pulse train exiting in the orthogonal polarization. The channel delay loop lengths were chosen to discretely fill the interpulse period of the original laser pulse train and the fiber stretchers provided fine temporal tuning to ensure a regularly spaced time-interweaved pulse train with an 8/spl times/ increased pulse repetition rate after the second pass through the WDM. The variable attenuators allowed the compensation of the input pulse spectral shape and provided equal optical power in each channel. We also show the spectrum of the sampler pulse train after amplification by an erbium-doped fiber amplifier. An 18 GHz LiNbO/sub 3/ integrated electrooptic modulator was used to amplitude modulate the pulse train with the RF signal to be digitized.