本論文提出一個具備串擾消除機制的光分碼多重存取(Optical code-division multiple-access, OCMDA)網路編碼/解碼架構。此架構的接收端主要由串接兩個陣列波導光柵(Arrayed-waveguide grating, AWG)建構而成，串接的陣列波導光柵結構會產生一個純串擾訊號。我們命名此純串擾項為「前鋒訊號」。由於前鋒訊號和每位使用者的接收訊號共用同一組陣列波導光柵編解碼裝置，故前鋒訊號的頻譜分布情形與帶內線性串擾拍差雜訊中的同調串擾雜訊項(In-band linear crosstalk noise)相同且兩者間具有近同調性,然而前鋒訊號與帶內線性串擾拍差雜訊的強度大小不同。故在進行串擾消除前，必須先將此前鋒訊號乘上合適的增益做調整，使前鋒訊號與帶內線性串擾拍差雜訊的強度相等。於是我們可以應用此調整後的前鋒訊號和訊號中帶內線性串擾拍差雜訊相減，來達到串擾消除的目的，減輕串擾效應造成的系統性能降級。
事實上，某些因素(例如:光源不平坦效應、非線性效應)可能會影響串擾拍差雜訊以及前鋒訊號間的同調性與振幅波動，如此在消除串擾拍差雜訊時，可能會發生「過消除」的情形。這些過消除的殘餘項會導致非同調串擾雜訊(Incoherent crosstalk)產生，進而造成系統中的非同調串擾雜訊增加。然而，即使非同調串擾雜訊增加了三倍，誤碼率分析結果顯示本論文提出的架構性能仍優於不具備串擾消除機制的架構的性能。模擬結果也顯示，藉由串擾消除架構，串擾拍差雜訊確實被抑制消除且性能亦得以改善。

This paper presents a compact optical code-division multiple-access (OCDMA) network coder-decoder (codec) with crosstalk reduction mechanism. The transmitter/receiver codecs is constructed based on cascaded dual AWGs which generate a pure crosstalk term, named a pilot signal in the paper.
The pilot signal has the same spectral distribution with every user’s coherent term of in-band crosstalk noise, but the intensity of pilot signal and crosstalk noise are different. In order to apply this pilot signal to eliminate the in-band linear crosstalk beat noise completely, the pilot signal should be multiplied by an appropriate gain and let the intensity of pilot signal equals to the intensity of crosstalk noise. After applying this pilot signal to subtract the crosstalk beat noise, crosstalk beat noise can be eliminated in real time and the performance degradation caused by crosstalk beat on AWGs can be eased off.
In general, some factors (e.g. non-flattened BLSs, non-linear effect) influence the amplitude and coherent nature between in-band linear crosstalk beat noise and pilot signal. The undeal situation might lead to over reducing and incoherent crosstalk. However, although the value of incoherent crosstalk is three times with our proposed scheme than the conventional scheme (optical CDMA network codecs structured with M-sequence codecs over waveguide-grating routers without crosstalk reduction mechanism), bit error rate (BER) shows that the performance of our proposed structure is better than that of the conventional scheme. Simulation results also indicate that crosstalk beat noise is eliminated to enhance the communication performance by crosstalk reduction mechanism.

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