One topic that has attracted attention is related to the behavior of the optical amplifiers under dynamic conditions, specifically because amplifiers working in a saturated condition produce power transients in all-optical reconfigurable WDM networks, e.g. adding/dropping channels. The goal of this work is to introduce the multiwavelength time-driven simulations technique, capable of simulation and analysis of transient effects in all-optical WDM networks with optical amplifiers, and allow the use of control schemes to avoid or minimize the impacts of transient effects in the system performance.
EDFAs have been used for some years now in building effective long-haul optical systems for the most diverse applications. For some applications, it is necessary to introduce some feedback control laws in order to avoid the generation of transients that could generate impairments in the system. In this paper, we use a multi-objective optimization approach based on genetic algorithms, to study the introduction of PD controllers into systems of cascaded EDFAs. We compare the use of individual controllers for each amplifier to the use of controllers to sets of amplifiers, and develop guidelines that help designers in making decisions while they are developing their own case-specific designs.
Raman fiber amplifiers (RFA) have been used in optical transmission communication systems in recent years due to their advantages over Erbium-doped fiber amplifiers (EDFA). Recently, the analysis of RFAs dynamic response and transient’s control has become important in order to predict system response to channel add/drop(s) or cable cuts in optical systems, and to avoid impairments caused by the power transients. Fast signal power transients in the surviving channels are caused by the cross-gain saturation effect in RFA, and the slope of the gain saturation characteristics determines the steady-state surviving channel power excursion. We are presenting the modeling and analysis of power transients control using two different approaches: (1) Power transient control using a Pump control method for a single and multi-pump scheme, and (2) the gain clamping of RFAs. Both methods are analyzed in a single amplifier as well in a cascade of RFAs.
We present the state of the art for commercial design and simulation software in the 'front end' of photonic circuit design. One recent advance is to extend the flexibility of the software by using more than one numerical technique on the same optical circuit. There are a number of popular and proven techniques for analysis of photonic devices. Examples of these techniques include the Beam Propagation Method (BPM), the Coupled Mode Theory (CMT), and the Finite Difference Time Domain (FDTD) method. For larger photonic circuits, it may not be practical to analyze the whole circuit by any one of these methods alone, but often some smaller part of the circuit lends itself to at least one of these standard techniques. Later the whole problem can be analyzed on a unified platform. This kind of approach can enable analysis for cases that would otherwise be cumbersome, or even impossible. We demonstrate solutions for more complex structures ranging from the sub-component layout, through the entire device characterization, to the mask layout and its editing. We also present recent advances in the above well established techniques. This includes the analysis of nano-particles, metals, and non-linear materials by FDTD, photonic crystal design and analysis, and improved models for high concentration Er/Yb co-doped glass waveguide amplifiers.