We consider the problem of routing uniform communication instances in switched optical rings that use wavelength-division multiplexing technology. A communication instance is called uniform if it consists exactly of all pairs of nodes in the graph whose distance is equal to one from a specified set S={d1,d2,…,dk}. When k=1 or 2, we prove necessary and sufficient conditions on the values in S relative to n for the optimal wavelength index to be equal to the optimal load in the ring Rn. When k=2, we show that for any uniform instance specified by {d1,d2}, there is an optimal wavelength assignment on the ring Rn, if n>(d1/q-2)d1+(d1/q-1)d2, where q=GCD(d1,d2). For general k and n, we show a -approximation for the optimal wavelength index; this is the best possible for arbitrary S. We also show that an optimal assignment can always be obtained provided n is large enough compared to the values in S. 相似文献
We present a thorough comparison of the characteristics of both tunable and multi-wavelength edge-emitting laser diodes. Both devices are currently seen as the most promising transmitters for future wavelength division multiplexing systems and networks. In our comparison, considerable attention is therefore paid to characteristics such as channel spacing and maximum number of channels and to frequency accuracy. Cost, stability and ease of use are other aspects which have been given attention, although they are not easily quantified. Because of their compactness and robustness, we only consider integrated devices. 相似文献
We propose and experimentally demonstrate an all-optical format conversion from two independent non-return-to-zero on-off keying (NRZ-OOK) signals to a return-to-zero quadrature phase shift keying (RZ-QPSK) signal using two cascaded SOAs. Within each SOA, the cross phase modulation (XPM) process is properly controlled by an assistant light. After evaluating its effect on XPM, a suitable power range of assistant light is chosen for the NRZ-OOK to RZ-QPSK format conversion. In the experiment, a RZ-QPSK signal is successfully obtained with opened demodulation eye-diagrams. 相似文献
The blocking probability in wavelength-routed all-optical networks is a very important measure of performance of the network. This blocking probability can be affected by many factors such as network topology, traffic load, number of links, algorithms employed and whether wavelength conversion is available or not. In this paper we have proposed a mathematical model to reduce the blocking probability of the WDM optical network for both wavelength convertible networks as well as for wavelength non-convertible networks. The model is can be used to evaluate the blocking performance of any network topology also it can be useful to improve its performance of the given network topology. 相似文献
Sufficient power margin is investigated for ten-channels WDM transmission over 68,908 km by using cascaded in-line semiconductor optical amplifier for the differential phase-shift keying (DPSK) modulation format for the first time. For this, we used the structural optimization and placement scheme of semiconductor optical amplifiers (SOAs) for long-haul WDM transmission. The SOA model for in-line amplifier has low crosstalk, ASE noise power and low noise figure with sufficient gain. The impact of noise figure, amplification factor, ASE noise power, optical gain and crosstalk with signal input power for the SOA model has been illustrated, which shows that 400 mA is the optimum bias current.
We observed that the optimized optical filter bandwidth for the 100 GHz channel spacing is 0.4 nm. We observe that as we decrease the channel spacing, the quality of signal is degraded. We show that the optimum span scheme-1 is used up to a transmission distance of 68,908 km with good quality for power margin more than 24 dB. This placement scheme of SOAs shows good power budget for long transmission distance. We show the optical spectrum and clear eye diagram at the transmission distance of 68,908 km for optimum span schemes. Finally, we investigate the maximum transmission distance with decrease in channel spacing, i.e., 20 and 50 GHz. 相似文献
Less than 100ps, polarization-independent switching operation of an active birefringent optical fiber loop filter using 1.3
μm control optical pulses as well as a 1.3 μm semiconductor optical amplifier (SOA) has been demonstrated. In the proposed
SOA-based active birefringent filter operating at 1.55 μm wavelength, 1.3 μm SOA is employed to control the polarization-mode
dispersion in the loop part. By injecting 1.3 μm ps gain-switched optical control pulses into the SOA, 1.5 μm input signals
can be switched from the transmission port to the reflection port with less than 100 ps rise time. 相似文献