Abstract:Authors demonstrate that a combination of feed-back control, feed-forward control, optical delay line and saturating channel can obtain the effective suppression of the transient effect in EDFA-based optical burst switched systems.
“…A saturating channel, constantly on, is added to keep the EDFA on when no traffic is present and to reduce the impact of transients [7]. The power of the saturating channel is between 5 to 9 dB higher than the power of a data channel (burst).…”
The benefits of adopting optical burst switching (OBS) in optical networks as well as the technological issues of the optical layer have been extensively studied. One of the challenges in developing commercial OBS systems is the use of the Erbium-Doped Fiber Amplifier (EDFA) technology to amplify bursty optical signals. A significant impairment in EDFA-based OBS systems is caused by the Spectral Hole Burning (SHB) of the EDFA. Due to this effect, the presence of a channel at a given wavelength induces a localised reduction in the EDFA gain spectrum that is a few nm wide ("a spectral hole"). An optical burst crossing an EDFA will require a certain amount of time to induce a hole in the gain spectrum; during this time the burst itself will therefore experience a variable gain. Under particular traffic conditions, this effect accumulates over a cascade of EDFAs resulting in large power excursions of the burst. In this paper the authors characterize the dynamics of SHB in OBS systems and describe its effect on the optical performance.
“…A saturating channel, constantly on, is added to keep the EDFA on when no traffic is present and to reduce the impact of transients [7]. The power of the saturating channel is between 5 to 9 dB higher than the power of a data channel (burst).…”
The benefits of adopting optical burst switching (OBS) in optical networks as well as the technological issues of the optical layer have been extensively studied. One of the challenges in developing commercial OBS systems is the use of the Erbium-Doped Fiber Amplifier (EDFA) technology to amplify bursty optical signals. A significant impairment in EDFA-based OBS systems is caused by the Spectral Hole Burning (SHB) of the EDFA. Due to this effect, the presence of a channel at a given wavelength induces a localised reduction in the EDFA gain spectrum that is a few nm wide ("a spectral hole"). An optical burst crossing an EDFA will require a certain amount of time to induce a hole in the gain spectrum; during this time the burst itself will therefore experience a variable gain. Under particular traffic conditions, this effect accumulates over a cascade of EDFAs resulting in large power excursions of the burst. In this paper the authors characterize the dynamics of SHB in OBS systems and describe its effect on the optical performance.
“…Figure 2 also shows the details of the ODNs, of the backhaul links and the details of the AN designs, such as amplifier gains and channel powers. It should be noted that in both architectures, all of the erbium-doped fiber amplifiers (EDFAs) used for upstream transmission are commercial devices with fast gain stabilization in order to reduce the impact of gain transients induced by the burst traffic [27]. Attenuators are added in the ODNs to emulate the end-of-life standard single mode fiber (SMF) attenuation (0.3dB/km) and realistic splitter losses including excess loss [28].…”
The continuing growth in information demand from fixed and mobile end-users, coupled with the need to deliver this content in an economically viable manner, is driving new innovations in access networks. In particular, it is becoming increasingly important to find new ways to enable the coexistence of heterogeneous services types which may require different signal modulation formats over the same fiber infrastructure. For example, the same physical layer can potentially be used to deliver shared 10Gb/s services to residential customers, dedicated point-to-point (P2P) 100Gb/s services to business customers, and wireless fronthaul, in a highly cost-effective manner. In this converged scenario, the performance of phase modulated signals can be heavily affected by nonlinear crosstalk from co-propagating on-off-keying (OOK) channels. In this paper, the overlay of a 100G P2P dual-polarization quadrature phase-shift keying (DP-QPSK) channel in a long-reach passive optical network (LR-PON) in the presence of co-propagating 10Gb/s OOK neighboring channels is studied for two different PON topologies. The first LR-PON topology is particularly suited for densely populated areas while the second is aimed at rural, sparsely populated areas. The experimental results indicate that with an emulated load of 40 channels the urban architecture can support up to 100km span and 512 users, while the rural architecture can support up to 120km span and 1024 users. Finally, a system model is developed to predict the system performance and system margins for configurations different from the experimental setups and to carry out design optimization that could in principle lead to even more efficient and robust schemes.
“…The upstream primary and secondary path EDFAs are each connected to a port of the 4×4 splitter, through a red/blue C-band filter in order to remove potential back-reflection from the high power downstream signals. All the EDFAs used in upstream are commercial devices with fast gain stabilization in order to reduce the impact of gain transients induced by the burst traffic [11].…”
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