Year: 2007
Radan Slavík, Ph.D., DSc.
Optical fibers are capable of transmitting up to 50 Tbit/s of data, while electronics-based systems operates generally at speeds below 100 GHz (typically 10 and 40 Gbit/s). To benefit from the capacity given by optical fibers, multiple (8-64) electronically processed signals carried using different wavelengths (channels) are usually combined (Wavelength Division Multiplexing, WDM). In this way, single-fiber capacity up to 2 Tbit/s is reached (typically 80-640 Gbit/s). However, increasing society demand for higher capacity, requires multiplexing of higher amount of channels (128,256,512, …), which requires extremely complex (and thus also expensive) systems. An alternative approach would be a combination of electronics-based signals in the temporal domain using optical means (Optical Time Division Multiplexing, OTDM) to generate data streams of 320 Gbit/s and higher at a single wavelength, and subsequent WDM of few (8-64) channels. To use OTDM, however, it is necessary to develop new ultrafast optical components and to suppress influence of different sources of noise (amplitude, frequency) that easily degrade ultrahigh capacity transmission systems.
In collaboration with EMT in Montreal, we developed one of the components necessary for robust OTDM systems – fiber filter for synthesis of ultrashort optical pulses with flat top temporal waveform [1,2]. The filters were fabricated in our institute - they are based on diffractive gratings ‘inscribed’ directly into an optical fiber. The flat-top pulses allows for significant suppression of the influence of the timing jitter, which we proved in collaboration with TU in Copenhagen [3,4]. We made the first demonstration of using flat-top pulses for OTDM systems operating at 320 Gbit/s [3] and 640 Gbit/s [4].
