光基礎設施的功率策略

　　光通信交換機構成了現代電信和數據通信基礎設施的主干。在過去的幾十年里，他們已經看到了建筑的巨大變化，因為它們變得越來越強大。

　　它們結合了高性能光學控制和基于最先進的半導體工藝的并行數字處理。其結果是，系統需要大量的功率域，其中許多功率域提供大電流和低電壓的組合。為了適應現代通信樞紐，電力系統需要高效率。隨著電壓的降低，對效率的要求迫使能量被傳遞給每個處理器和光收發模塊。

　　原來，電信系統采用集中的權力結構，與AC轉換為?48 VDC的前端整流器送一套DC /直流轉換器。大電流母線將所需電壓路由到機柜內部的每一個擱板，其中包含用于交換的線路卡。公共汽車不僅笨重，而且價格昂貴，而且很難對供應實行監管。

　　在20世紀90年代，許多電信系統使用的電力傳輸架構改變為一種分布式電源架構，其中48 V電源被送到更多的本地DC / DC轉換器，在本地線路卡和其他計算元件上安裝。這種趨勢是由電壓的逐漸降低和電流的增加以及對功率順序的控制來實現模塊的熱交換而驅動的。

　　The distributed-power architecture was devised on the assumption there would typically be just one， or maybe two， different load voltages per board. For most 48 V systems， providing isolation between the higher distribution voltage and the target-voltage is a requirement. Isolated converters tend to be larger and more expensive than their non-isolated equivalents. The isolation stage calls for a transformer whereas most non-isolated designs can simply use an inductor. Also， the PCB design of the converter is more complex， as isolation barriers are needed between the control signals that pass between the primary and secondary side that the converter circuitry needs to provide accurate control.

　　However， even the distributed-power architecture limits flexibility in terms of the number of rails that can be supported. Providing for more than two output voltages with isolated converters requires significant amounts of space and rapidly becomes expensive. The high-density field-programmable gate arrays （FPGAs） and processors used in optical-networking systems often have complex power requirements， involving a large number of low-voltage supply rails. For example， the serial transceivers used on high-density FPGAs will have different requirements to those used for the core fabric， which may be different from those used for general-purpose I/O.