An all-optical upstream carrier generation scheme based on a Brillouin/erbium fiber laser (BEFL) is proposed for wavelength-independent optical network units in a wavelength-division multiplexed passive optical network. Experimental measurements show that the BEFL mainly operates in a single longitudinal mode and occasionally undergoes mode hopping given environmental fluctuations. Employing the proposed scheme, bidirectional transmission at 1.25-Gb/s over 20-km single-mode fiber is performed. Bit error rate measurement shows no crosstalk originating from Rayleigh backscattering and back-reflections in the network, due to a 0.08-nm-wavelength shift between the downstream and upstream carriers.
All-optical virtual private network (VPN), which offers dedicated optical channels to connect users within a VPN group,
is considered a promising approach to efficient internetworking with low latency and enhanced security implemented in
the physical layer. On the other hand, time-division multiplexed (TDM) / wavelength-division multiplexed (WDM)
network architecture based on a feeder-ring with access-tree topology, is considered a pragmatic migration scenario from
current TDM-PONs to future WDM-PONs and a potential convergence scheme for access and metropolitan networks,
due to its efficiently shared hardware and bandwidth resources. All-optical VPN internetworking in such a metro-access
integrated structure is expected to cover a wider service area and therefore is highly desirable. In this paper, we present a
TDM/WDM metro-access integrated network supporting all-optical VPN internetworking among ONUs in different sub-
PONs based on orthogonal differential-phase-shift keying (DPSK) / amplitude-shift keying (ASK) modulation format. In
each ONU, no laser but a single Mach-Zehnder modulator (MZM) is needed for the upstream and VPN signal generation,
which is cost-effective. Experiments and simulations are performed to verify its feasibility as a potential solution to the
future access service.
Optical fiber parametric amplification is combined with Raman amplification to demonstrate the possibility of extending
the flat gain bandwidth of Raman fiber amplifiers. Counter propagating pumps separated by over 145 nm are used to
pump a section of highly nonlinear fiber. Parametric gain enables an increase in the gain bandwidth by extending the
gain region to the long wavelength side of the Raman gain. Gains of nearly 20 dB have been achieved with this
configuration. To achieve gain flatness of 5-6 dB, lower peak gains of between 8 and 14 dB are observed where the
variations of the gain and gain flatness are controlled by adjusting the two pump powers. Optimal pump powers are
determined that result in good performance amplification by characterizing the receiver power penalty of bit error rate
measurements. Negligible power penalty is observed in the region of strong Raman gain whereas nearly a 3 dB power
penalty is observed in the region of strong parametric gain. An experimental technique is proposed that helps in the
understanding of the coupling of the parametric and Raman processes.
In this paper, a novel in-band optical spectra and filter shape monitoring technique is experimentally demonstrated. Based on swept coherent detection, the proposed technique simultaneously measures the signal and ASE spectra by adjusting the polarization states of the signal and local oscillator. In our experiment, a high resolution of 0.002 nm is achieved.
Based on the analyses of the key limiting factors for duobinary signals in dispersion limited fiber systems, we propose a novel optical receiver design that can further overcome the deterministic timing 'jitter' resulted from the dispersion-induced inter-symbol interference. Our idea is based on over-sampling of the received waveform and a novel decoding scheme. Our technique would provide better estimations of the received bits based on a decision feedback and feedforward scheme that takes advantage of the knowledge of adjacent bits. We study, through extensive simulations, the effectiveness of our novel receiver design in increasing the dispersion tolerance, and our promising results show that our innovative solution can provide significantly improvement over even the best reported schemes thus far.
Recent laboratory experiments have demonstrated that distributed Raman amplification, advanced modulation formats, optimized dispersion maps, and forward error correction are key technologies for 10-Gb/s and 40-Gb/s DWDM terrestrial transmission over 2000 to 6000 km. The transmission fiber's Raman gain efficiency and dispersion properties are thus important parameters. Future high-bit-rate, high-capacity installed systems will require advanced transmission fibers to extend their reach to at least 2000 km, a distance also specified by a high-profile U.S. government optical networking project. This paper will address a number of the enabling fiber properties, including dispersion, dispersion slope, Raman gain efficiency, and polarization mode dispersion. In addition, several recent experiments will be reviewed, including demonstrations of high-spectral-efficiency terrestrial transmission at 10 Gb/s and 40 Gb/s over 4000 km and 3200 km, respectively, and 10-Gb/s transmission over 2400 km using 200-km spans.
Raman amplification has been one of the enabling technologies employed to push the capacity x distance product in terrestrial DWDM systems. Due to its broad gain spectrum and the commercial availability of desired Raman pump wavelengths, more than 100-nm bandwidth is made possible covering the low loss window of silica fibers. In addition, distributed Raman amplification in transmission fibers and/or dispersion-compensating fibers (DCF) can significantly improve the system signal-to-noise ratio. In this talk, we will discuss the advantages and issues of Raman amplification, including pump-pump and pump-signal crosstalk, and their impact on the design of next generation fibers. Recent transmission experiments over Raman enabled fibers will be presented. Optimization of the system performance by allocating the Raman gains in co-, counter- and DCF-pumping will also be discussed.
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