Demonstration of negative dispersion fibers for DWDM metropolitan area networks

Abstract

In this paper, we present a detailed experimental and theoretical study, showing that a novel nonzero dispersion-shifted fiber with negative dispersion enhances the capabilities of metropolitan area optical systems, while at the same time, reducing the system cost by eliminating the need of dispersion compensation. The performance of this dispersion-optimized fiber was studied using different types of optical transmitters for both 1310-and 1550-nm wavelength windows and for both 2.5and 10-Gb/s bit rates. It is shown that this new fiber extends the nonregenerated distance up to 300 km when directly modulated distributed feedback (DFB) laser transmitters at 2.5 Gb/s are used. The negative dispersion characteristics of the fiber also enhance the transmission performance in metropolitan area networks with transmitters that use electroabsorption (EA) modulator integrated distributed feedback (DFB) lasers, which are biased for positive chirp. In the case of 10 Gb/s, externally modulated signals (using either EA-DFBs or external modulated lasers using Mach-Zehnder modulators), we predict that the maximum reach that can be accomplished without dispersion compensation is more than 200 km for both 100-and 200-GHz channel spacing. To our knowledge, this is the first demonstration of the capabilities of a nonzero dispersion-shifted fiber with negative dispersion for metropolitan applications.

Free-Running 1550 nm VCSEL for 107 Gb/s Transmission in 997 km PON

“…The signal observations at the outputs of the 50 km (MS1) and 99.7 km (cascaded MS1 and MS2) lengths of dispersion-matched fiber indicate good signal recovery at the receiver; clear open eyes and good OSNRs were observed. An improved extinction ratio was observed after the 99.7 km of cascaded fiber: the net negative chromatic dispersion of the link improves the directly modulated optical signal from the laser; this observation agrees well with other reports [17]. The OSNR was, however, degraded by 2.38 dB by transmission along MS1, and a further 0.36 dB by transmission over the second matched span (MS2).…”

“…With the IDF, we were able to recover error-free transmissions for all PRBSs used. The net negative dispersion of the matched transmission spans was observed to improve transmission performance beyond that obtained at the transmitter output; this result does not conflict with previously reported results for transmission of directly modulated laser signals over links with net negative chromatic dispersion [17].…”

Modeling dispersion in optical fibers: applications to dispersion tailoring and dispersion compensation

“…Indeed special fiber designs have been developed which have normal dispersion in the 1550-nm region and hence can be used with chirped directly modulated lasers for extended propagation distances without suffering from dispersive effects. Such fibers could be very interesting especially in metro networks [19].…”

“…(19)] by τ rms = τ / √ 2. For a communication system working at a bit rate of B bits per second, the bit period is 1/B s. In order to keep the interference between adjacent bits below a specified level, the rms width of the dispersed pulse needs to be kept below a certain fraction of the bit period B.…”

Effects of Dispersion Fiber on CWDM Directly Modulated System Performance

“…A number of approaches have been used to improve transmission performance using directly modulated lasers, including cutting down the chirp externally using a narrow bandpass filter [Yan 2005] and the deployment of a negative dispersion fiber [Tomkos 2001a, Tomkos 2002. However, typical metro and access networks are made up of a conventional single-mode fiber (SMF) and because of the cost and difficulty (or lack of feasibility) in changing embedded fiber links, a method that enhances system performance requiring only the modification of one or both of the endpoints of a link is a critical requirement.…”