Abstract-A uniform 35-nm-wide spectrum is generated by broadening the output from a 2.5-GHz mode-locked femtosecond fiber laser in dispersion shifted fiber. The obtained spectrum is suitable for spectral slicing and wavelength-division-multiplexed applications. The spectral broadening in dispersion shifted fiber is optimized as a function of the launched pulse chirp parameter.Index Terms-High-repetition-rate mode-locked laser, modelocked fiber laser, optical fiber dispersion, optical fiber nonlinearity, pulse propagation in optical fiber, spectral slicing wavelengthdivision multiplexing, wavelength-division multiplexing.
BROAD-BAND transmitters with multigigahertz data rates operating in the 1550-nm fiber-optic communications band are key enabling technologies for future wavelength and time division multiplexed (wavelength-division multiplexing and time-division multiplexing) networks. As the number of wavelength channels and data rates grow, using a separate stabilized source for each channel may become less practical. The individual CW sources must be tuned and aligned with the specific wavelength grid of the system. The use of a single, high repetition rate mode-locked erbium-doped fiber (EDF) laser simplifies wavelength stabilization and provides a potentially attractive alternative since its broad output spectrum can be partitioned into a large number of WDM channels [1], [2]. The wavelength channels are selected by passive filtering which facilitates the addition of new channels, and minimizes the affect of wavelength drift on system performance [3], [4]. In comparison with broadened incoherent sources such as those based on amplified spontaneous emission or supercontinuum generation, mode-locked sources do not suffer from beat noise between different portions of the spectrum within a channel, which can limit transmission capacity [5]- [7]. The coherence of the mode-locked source can be used to increase the channel information capacity by techniques such as those used in codedivision multiple-access (CDMA) networks [8]. Even higher bitrates per channel can be achieved by time multiplexing the short transform limited (picosecond) pulses generated in each of the spectrally sliced channels.In this letter, we report the generation of a uniform and flat, 35-nm-wide spectrum centered at 1549 nm from a 2.5-GHz repetition rate, femtosecond fiber laser. For channel
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