Design of Compact and Scalable Wavelength-Exchanging Cross Connects

[[abstract]]在分波多工網路中，有個重要元件稱為：波長交叉連結器。基本上，它是個外接波長轉換器的光交叉連結器。最近有文獻提出：能同時實現空間交換、以及波長轉換之光交叉連結器，稱為波長調換交叉連結器，來有效的減少硬體複雜度。我們從中觀察到：光交叉連結器(含：波長調換交叉連結器)的設計，是基於要達到交換不阻塞之目的，而提供完全排列的連結。亦即是任何一個輸入埠之訊號，都可以連結到任何一個輸出埠。這將可能產生下列現象：多個來自同一輸入光纖的不同的波長信號，經過交叉連結器輸出時，可能輸出到同一條光纖去，並且互相轉換彼此的波長。這樣的互相轉換彼此的波長，在分波多工網路中或許是不需要的。本計畫提出：基於光纖之間的排列（稱為充分排列），而非基於埠間的排列（稱為完全排列），來設計具有精簡的（即有低硬體元件複雜度）暨可擴充的（即有規則性的結構）波長調換交叉連結器。最初，我們先針對具有 2 條光纖，而每條光纖有數條波長的波長調換交叉連結器來設計。至於設計的方法，本計畫提出的方法與步驟為：(1)利用排列矩陣來描述：波長調換交叉連結器中22 元件的運作；(2)應用排列矩陣的乘積法則，來排列某些基礎的22 元件，使其實現其他元件的運作；(3)使用這些基礎的22 元件，來建構波長調換交叉連結器；(4)利用數學歸納法，來推導有規則性的結構。[[abstract]]In wavelength division multiplexing (WDM) networks, wavelength cross-connect (WXC) is an important element, which is basically the optical cross-connect with external stage of wavelength converters. Recently, a new type of WXC, namely wavelength-exchanging cross-connect (WEX), was proposed. Since WEX can simultaneously perform switching and wavelength converting, it has low hardware complexity. We observe that, to achieve switching nonblocking, the designs of existing WXCs (including WEXs) are based on full-permutation switching, which provides any permutation of input signals at the output of the cross-connect. This may result in the fact that some different wavelengths coming from a fiber will be routed to a particular fiber, and also performed wavelength converting among themselves. Such permutations may not be necessary in a WDM network. We propose designing compact (with low hardware complexity) and scalable (with regular structure) WEXs, which is based on the permutations among output fibers (namely sufficient permutations), but not among output ports (namely full permutations). Initially, we will focus on the WEX with 2 fibers and several wavelengths in each fiber. On the design of such WEXs, we propose the method of: (i) using a permutation matrix to describe the operation of a 22 element in a WEX; (ii) applying some permutation matrix product rules to lineup particular 22 elements (called fundamental elements) so that they can perform the same operation of the other 22 elements; (iii) employing fundamental elements to construct a WEX and (iv) deriving the regular structures of a WEX by mathematical induction.[[note]]NSC100-2221-E327-03