Wideband delays generated in an all-optical tunable delay line, preserving signal wavelength and bandwidth

Abstract

A novel technique to produce large all-optically controlled tunable delays of 100 ps pulse train in optical fibers is demonstrated. The configuration of the delay line basically consists of two main stages: the wavelength conversion via semiconductor optical amplifiers and the group velocity delaying via a dispersive optical medium. The wavelength-converted signal was precisely delayed over a wide temporal range from picoseconds to nanoseconds using a dispersive fiber, preserving the wavelength and the bandwidth of the signal. 100 ps FWHM signal pulses were delayed continuously up to 14 ns with moderate pulse distortion, corresponding to a 140-bit delay.

Tunable photonic delay lines in optical fibers

“…In a first stage, the wavelength of a signal pulse is converted into another target wavelength using wavelength conversion. Then the wavelength-converted pulse propagates through an optical medium showing a large overall dispersion, such as long segments of optical fiber [30,32,33,45,50,79] or a highly chirped fiber Bragg grating [49]. Due to the intrinsic chromatic dispersion of the medium, the incident pulse emerges from the dispersive element with a relative time delay when compared to the transit time as it would be at the original wavelength of the pulse.…”

“…The PPLN wavelength convertor improves the performance of signal delaying in terms of a reduced additive noise, a faster reconfiguration time and a larger maximum achievable delay since the wavelength tuning range is inherently more extended. Following the same motivation for a more efficient conversion, in a recent work [32] cross gain modulation in a semiconductor optical amplifier has been implemented to efficiently realize the wavelength conversion using a low pump power level and over a broad wavelength range.…”

Photonic delay line for broadband optical signals, based on dynamic grating reflectors in fibers

“…First, slow and fast lightbased delaying scheme offers a flexible timing tool, but the maximum achievable time delay is inherently limited due to a large dispersion induced by a spectral resonance, presenting a critical bottleneck in terms of optical storage capacity [2][3] . Secondly, dispersive delay line based on group velocity dispersion in optical media was proposed and improved by a large increment the fractional delay [4][5][6] . However, this scheme still suffers from signal distortion since the chromatic dispersion is a key parameter to control the amount of time delay, so limiting the signal bandwidth.…”