Browsing by Subject "Timing jitter"

Now showing 1 - 3 of 3

Open Access
An integrated femtosecond timing distribution system for XFELS
(Massachusetts Institute of Technology, 2006) Kim, J.; Burnham, J.; Chen, J.; Kartner, F. X.; İlday, Fatih Ömer; Ludwig, F.; Schlarb, H.; Winter, A.; Ferianis, M.; Cheever, D.
Tightly synchronized lasers and RF-systems with timing jitter in the few femtoseconds range are necessary sub-systems for future X-ray free electron laser facilities. In this paper, we present an optical-microwave phase detector that is capable of extracting an RF-signal from an optical pulse stream without amplitude-to-phase conversion. Extraction of a microwave signal with 3 fs timing jitter (from 1 Hz to 10 MHz) from an optical pulse stream is demonstrated. Scaling of this component to subfemtosecond resolution is discussed. Together with low noise mode-locked lasers, timing-stabilized optical fiber links and compact optical cross-correlators, a flexible femtosecond timing distribution system with potentially sub-10 fs precision over distances of a few kilometers can be constructed. Experimental results on both synchronized RF and laser sources will be presented.
Open Access
The tradeoff between processing gains of an impulse Radio UWB system in the presence of timing jitter
(Institute of Electrical and Electronics Engineers, 2007) Gezici, Sinan; Molisch, A. F.; Poor, H.V.; Kobayashi, H.
In time hopping impulse radio, Nf pulses of duration Tc are transmitted for each information symbol. This gives rise to two types of processing gains: i) pulse combining gain, which is a factor Nf, and (ii) pulse spreading gain, which is Nc=Tf/Tc, where Tf is the mean interval between two subsequent pulses. This paper investigates the tradeoff between these two types of processing gains in the presence of timing jitter. First, an additive white Gaussian noise (AWGN) channel is considered, and approximate closed-form expressions for bit error probability (BEP) are derived for impulse radio systems with and without pulse-based polarity randomization. Both symbol-synchronous and chip-synchronous scenarios are considered. The effects of multiple-access interference (MAI) and timing jitter on the selection of optimal system parameters are explained through theoretical analysis. Finally, a multipath scenario is considered, and the tradeoff between processing gains of a synchronous impulse radio system with pulse-based polarity randomization is analyzed. The effects of the timing jitter, MAI, and interframe interference (IFI) are investigated. Simulation studies support the theoretical results.
Open Access
Ultra-low timing-jitter passively mode-locked fiber lasers for long-distance timing synchronization
(SPIE, 2006) İlday, F. Ömer; Winter, A.; Kim J.-W.; Chen, J.; Schmüser, P.; Schlarb, H.; Kärtner, F. X.
One of the key challenges for the next-generation light sources such as X-FELs is to implement a timing stabilization and distribution system to enable ∼ 10 fs synchronization of the different RF and laser sources distributed in such facilities with distances up to a few kilometers. These requirements appear to be beyond the capability of traditional RF distribution systems based on temperature-stabilized coaxial cables. A promising alternative is to use an optical transmission system: A train of pulses generated from a laser with low timing jitter is distributed over length-stabilized fiber links to remote locations. The repetition frequency of the pulse train and its higher harmonics contain the synchronization information. At the remote locations, RF signals are extracted simply by using a photodiode and a suitable bandpass filter to pick the desired harmonic of the laser repetition rate. Passively mode-locked Er-doped fiber lasers provide excellent long-term stability. The laser must have extremely low timing jitter, particularly at high frequencies (>1 kHz). Ultimately, the timing jitter is limited by quantum fluctuations in the number of photons making up the pulse and the incoherent photons added in the cavity due to spontaneous emission. The amplitude and phase noise of a home-built laser, generating 100-fs, 1-nJ pulses, was characterized. The measured phase noise (timing jitter) is sub-10 fs. from 1 kHz to Nyquist frequency. In addition to synchronization of accelerators, the ultra-low timing jitter pulse source can find applications in next-generation telecommunication systems.